feat: 新增关于、常见问题、反馈和套餐详情屏幕

- 新增AboutScreen关于页面
- 新增FAQScreen常见问题页面
- 新增FeedbackScreen反馈页面
- 新增PlanDetailsScreen套餐详情页面
- 新增工具类（DateUtils、TextUtils、ValidationUtils）

app-android/app/src/main/java/com/huaga/life_echo/ui/screens/AboutScreen.kt

@@ -0,0 +1,157 @@
+package com.huaga.life_echo.ui.screens
+
+import androidx.compose.foundation.layout.*
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.*
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+import com.huaga.life_echo.ui.icons.AppIcons
+import com.huaga.life_echo.ui.theme.LightPurple
+
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun AboutScreen(
+    navController: androidx.navigation.NavHostController? = null
+) {
+    Scaffold(
+        topBar = {
+            TopAppBar(
+                title = { Text("关于我们") },
+                navigationIcon = {
+                    IconButton(onClick = { navController?.popBackStack() }) {
+                        Icon(
+                            imageVector = AppIcons.ArrowBack,
+                            contentDescription = "返回",
+                            tint = Color.White
+                        )
+                    }
+                },
+                colors = TopAppBarDefaults.topAppBarColors(
+                    containerColor = LightPurple,
+                    titleContentColor = Color.White,
+                    navigationIconContentColor = Color.White
+                )
+            )
+        }
+    ) { paddingValues ->
+        Column(
+            modifier = Modifier
+                .fillMaxSize()
+                .padding(paddingValues)
+                .verticalScroll(rememberScrollState())
+                .padding(24.dp),
+            horizontalAlignment = Alignment.CenterHorizontally
+        ) {
+            // Logo 或图标区域
+            Box(
+                modifier = Modifier
+                    .size(120.dp)
+                    .padding(bottom = 24.dp),
+                contentAlignment = Alignment.Center
+            ) {
+                Icon(
+                    imageVector = AppIcons.Info,
+                    contentDescription = "应用图标",
+                    tint = LightPurple,
+                    modifier = Modifier.size(80.dp)
+                )
+            }
+            
+            // 应用名称
+            Text(
+                text = "Life Echo",
+                fontSize = 28.sp,
+                fontWeight = FontWeight.Bold,
+                color = MaterialTheme.colorScheme.onSurface,
+                modifier = Modifier.padding(bottom = 8.dp)
+            )
+            
+            // 版本信息
+            Text(
+                text = "版本 1.0.0",
+                fontSize = 16.sp,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+                modifier = Modifier.padding(bottom = 32.dp)
+            )
+            
+            Divider(
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .padding(vertical = 16.dp),
+                color = MaterialTheme.colorScheme.outlineVariant
+            )
+            
+            // 应用介绍
+            Text(
+                text = "应用介绍",
+                fontSize = 20.sp,
+                fontWeight = FontWeight.Bold,
+                color = MaterialTheme.colorScheme.onSurface,
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .padding(bottom = 12.dp)
+            )
+            
+            Text(
+                text = "Life Echo 是一款智能回忆录助手应用，帮助您记录和整理生活中的美好回忆。通过AI对话的方式，轻松创建属于您的个人回忆录。",
+                fontSize = 16.sp,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .padding(bottom = 24.dp),
+                lineHeight = 24.sp
+            )
+            
+            Divider(
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .padding(vertical = 16.dp),
+                color = MaterialTheme.colorScheme.outlineVariant
+            )
+            
+            // 联系方式
+            Text(
+                text = "联系我们",
+                fontSize = 20.sp,
+                fontWeight = FontWeight.Bold,
+                color = MaterialTheme.colorScheme.onSurface,
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .padding(bottom = 12.dp)
+            )
+            
+            Text(
+                text = "如有任何问题或建议，欢迎通过应用内的"反馈与客服"功能联系我们。",
+                fontSize = 16.sp,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .padding(bottom = 24.dp),
+                lineHeight = 24.sp
+            )
+            
+            Divider(
+                modifier = Modifier
+                    .fillMaxWidth()
+                    .padding(vertical = 16.dp),
+                color = MaterialTheme.colorScheme.outlineVariant
+            )
+            
+            // 版权信息
+            Text(
+                text = "© 2024 Life Echo. All rights reserved.",
+                fontSize = 14.sp,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+                modifier = Modifier.padding(top = 16.dp)
+            )
+            
+            Spacer(modifier = Modifier.height(32.dp))
+        }
+    }
+}

app-android/app/src/main/java/com/huaga/life_echo/ui/screens/FAQScreen.kt

@@ -0,0 +1,89 @@
+package com.huaga.life_echo.ui.screens
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.layout.*
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.foundation.lazy.items
+import androidx.compose.material3.*
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+import androidx.lifecycle.viewmodel.compose.viewModel
+import com.huaga.life_echo.ui.components.common.EmptyStateView
+import com.huaga.life_echo.ui.components.common.LoadingIndicator
+import com.huaga.life_echo.ui.components.profile.FAQItem
+import com.huaga.life_echo.ui.icons.AppIcons
+import com.huaga.life_echo.ui.theme.LightPurple
+import com.huaga.life_echo.ui.viewmodel.ProfileViewModel
+import com.huaga.life_echo.ui.viewmodel.ViewModelFactory
+
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun FAQScreen(
+    navController: androidx.navigation.NavHostController? = null,
+    viewModel: ProfileViewModel = viewModel(
+        factory = ViewModelFactory(LocalContext.current)
+    )
+) {
+    val faqs by viewModel.faqs.collectAsState()
+    val isLoading by viewModel.isLoading.collectAsState()
+    
+    Scaffold(
+        topBar = {
+            TopAppBar(
+                title = { Text("常见问题") },
+                navigationIcon = {
+                    IconButton(onClick = { navController?.popBackStack() }) {
+                        Icon(
+                            imageVector = AppIcons.ArrowBack,
+                            contentDescription = "返回",
+                            tint = Color.White
+                        )
+                    }
+                },
+                colors = TopAppBarDefaults.topAppBarColors(
+                    containerColor = LightPurple,
+                    titleContentColor = Color.White,
+                    navigationIconContentColor = Color.White
+                )
+            )
+        }
+    ) { paddingValues ->
+        when {
+            isLoading -> {
+                LoadingIndicator(modifier = Modifier.padding(paddingValues))
+            }
+            faqs.isEmpty() -> {
+                EmptyStateView(
+                    message = "暂无常见问题",
+                    icon = "❓",
+                    modifier = Modifier.padding(paddingValues)
+                )
+            }
+            else -> {
+                LazyColumn(
+                    modifier = Modifier
+                        .fillMaxSize()
+                        .padding(paddingValues)
+                        .background(MaterialTheme.colorScheme.background),
+                    contentPadding = PaddingValues(16.dp),
+                    verticalArrangement = Arrangement.spacedBy(12.dp)
+                ) {
+                    items(
+                        items = faqs,
+                        key = { faq -> faq.id }
+                    ) { faq ->
+                        FAQItem(faq = faq)
+                    }
+                }
+            }
+        }
+    }
+}

app-android/app/src/main/java/com/huaga/life_echo/ui/screens/FeedbackScreen.kt

@@ -0,0 +1,96 @@
+package com.huaga.life_echo.ui.screens
+
+import androidx.compose.foundation.layout.*
+import androidx.compose.foundation.layout.wrapContentHeight
+import androidx.compose.material3.*
+import androidx.compose.runtime.*
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+import androidx.lifecycle.viewmodel.compose.viewModel
+import com.huaga.life_echo.ui.components.profile.FeedbackForm
+import com.huaga.life_echo.ui.icons.AppIcons
+import com.huaga.life_echo.ui.theme.LightPurple
+import com.huaga.life_echo.ui.viewmodel.ProfileViewModel
+import com.huaga.life_echo.ui.viewmodel.ViewModelFactory
+
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun FeedbackScreen(
+    navController: androidx.navigation.NavHostController? = null,
+    viewModel: ProfileViewModel = viewModel(
+        factory = ViewModelFactory(LocalContext.current)
+    )
+) {
+    var showSuccessDialog by remember { mutableStateOf(false) }
+    
+    Scaffold(
+        topBar = {
+            TopAppBar(
+                title = { Text("反馈与客服") },
+                navigationIcon = {
+                    IconButton(onClick = { navController?.popBackStack() }) {
+                        Icon(
+                            imageVector = AppIcons.ArrowBack,
+                            contentDescription = "返回",
+                            tint = Color.White
+                        )
+                    }
+                },
+                colors = TopAppBarDefaults.topAppBarColors(
+                    containerColor = LightPurple,
+                    titleContentColor = Color.White,
+                    navigationIconContentColor = Color.White
+                )
+            )
+        }
+    ) { paddingValues ->
+        Column(
+            modifier = Modifier
+                .fillMaxSize()
+                .padding(paddingValues)
+                .padding(16.dp)
+        ) {
+            FeedbackForm(
+                onSubmit = { content, contact ->
+                    viewModel.submitFeedback(
+                        content = content,
+                        contact = contact,
+                        onSuccess = {
+                            showSuccessDialog = true
+                        },
+                        onError = { }
+                    )
+                }
+            )
+        }
+        
+        // 提交成功对话框
+        if (showSuccessDialog) {
+            AlertDialog(
+                onDismissRequest = { showSuccessDialog = false },
+                title = { Text("提交成功") },
+                text = { 
+                    Text(
+                        text = "感谢您的反馈，我们会尽快处理！",
+                        modifier = Modifier.wrapContentHeight()
+                    )
+                },
+                confirmButton = {
+                    TextButton(
+                        onClick = {
+                            showSuccessDialog = false
+                            navController?.popBackStack()
+                        }
+                    ) {
+                        Text("确定", color = LightPurple)
+                    }
+                }
+            )
+        }
+    }
+}

app-android/app/src/main/java/com/huaga/life_echo/ui/screens/PlanDetailsScreen.kt

@@ -0,0 +1,77 @@
+package com.huaga.life_echo.ui.screens
+
+import androidx.compose.foundation.background
+import androidx.compose.foundation.layout.*
+import androidx.compose.foundation.lazy.LazyColumn
+import androidx.compose.material3.*
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.collectAsState
+import androidx.compose.runtime.getValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.graphics.Color
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.text.font.FontWeight
+import androidx.compose.ui.unit.dp
+import androidx.compose.ui.unit.sp
+import androidx.lifecycle.viewmodel.compose.viewModel
+import com.huaga.life_echo.ui.components.common.LoadingIndicator
+import com.huaga.life_echo.ui.components.payment.PlanCard
+import com.huaga.life_echo.ui.components.profile.PlanDetailsCard
+import com.huaga.life_echo.ui.icons.AppIcons
+import com.huaga.life_echo.ui.theme.LightPurple
+import com.huaga.life_echo.ui.viewmodel.PaymentViewModel
+import com.huaga.life_echo.ui.viewmodel.ViewModelFactory
+
+@OptIn(ExperimentalMaterial3Api::class)
+@Composable
+fun PlanDetailsScreen(
+    navController: androidx.navigation.NavHostController? = null,
+    viewModel: PaymentViewModel = viewModel(
+        factory = ViewModelFactory(LocalContext.current)
+    )
+) {
+    val currentPlan by viewModel.currentPlan.collectAsState()
+    val isLoading by viewModel.isLoading.collectAsState()
+    
+    Scaffold(
+        topBar = {
+            TopAppBar(
+                title = { Text("套餐详情") },
+                navigationIcon = {
+                    IconButton(onClick = { navController?.popBackStack() }) {
+                        Icon(
+                            imageVector = AppIcons.ArrowBack,
+                            contentDescription = "返回",
+                            tint = Color.White
+                        )
+                    }
+                },
+                colors = TopAppBarDefaults.topAppBarColors(
+                    containerColor = LightPurple,
+                    titleContentColor = Color.White,
+                    navigationIconContentColor = Color.White
+                )
+            )
+        }
+    ) { paddingValues ->
+        if (isLoading) {
+            LoadingIndicator(modifier = Modifier.padding(paddingValues))
+        } else {
+            LazyColumn(
+                modifier = Modifier
+                    .fillMaxSize()
+                    .padding(paddingValues)
+                    .background(MaterialTheme.colorScheme.background),
+                contentPadding = PaddingValues(16.dp),
+                verticalArrangement = Arrangement.spacedBy(16.dp)
+            ) {
+                currentPlan?.let { plan ->
+                    item {
+                        PlanDetailsCard(plan = plan)
+                    }
+                }
+            }
+        }
+    }
+}

app-android/app/src/main/java/com/huaga/life_echo/utils/AnimationUtils.kt

@@ -0,0 +1,71 @@
+package com.huaga.life_echo.utils
+
+import androidx.compose.animation.core.*
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.draw.alpha
+import androidx.compose.ui.draw.scale
+
+/**
+ * 动画工具类
+ */
+object AnimationUtils {
+    
+    /**
+     * 创建打字机效果的动画值
+     */
+    @Composable
+    fun createTypingAnimation(
+        durationMillis: Int = 1000,
+        delayMillis: Int = 0
+    ): androidx.compose.runtime.State<Float> {
+        val infiniteTransition = rememberInfiniteTransition(label = "typing")
+        return infiniteTransition.animateFloat(
+            initialValue = 0f,
+            targetValue = 1f,
+            animationSpec = infiniteRepeatable(
+                animation = tween(durationMillis, delayMillis, FastOutSlowInEasing),
+                repeatMode = RepeatMode.Reverse
+            ),
+            label = "typing_alpha"
+        )
+    }
+    
+    /**
+     * 创建脉冲动画
+     */
+    @Composable
+    fun createPulseAnimation(
+        durationMillis: Int = 1000
+    ): androidx.compose.runtime.State<Float> {
+        val infiniteTransition = rememberInfiniteTransition(label = "pulse")
+        return infiniteTransition.animateFloat(
+            initialValue = 0.8f,
+            targetValue = 1f,
+            animationSpec = infiniteRepeatable(
+                animation = tween(durationMillis, easing = FastOutSlowInEasing),
+                repeatMode = RepeatMode.Reverse
+            ),
+            label = "pulse_scale"
+        )
+    }
+}
+
+/**
+ * 打字机效果修饰符
+ */
+@Composable
+fun Modifier.typingEffect(visible: Boolean): Modifier {
+    val alpha by AnimationUtils.createTypingAnimation()
+    return this.alpha(if (visible) alpha else 1f)
+}
+
+/**
+ * 脉冲效果修饰符
+ */
+@Composable
+fun Modifier.pulseEffect(): Modifier {
+    val scale by AnimationUtils.createPulseAnimation()
+    return this.scale(scale)
+}

app-android/app/src/main/java/com/huaga/life_echo/utils/PaymentUtils.kt

@@ -0,0 +1,71 @@
+package com.huaga.life_echo.utils
+
+/**
+ * 支付工具类
+ * 用于处理支付相关的工具函数
+ */
+object PaymentUtils {
+    
+    /**
+     * 格式化价格
+     * @param price 价格
+     * @param currency 货币符号
+     * @return 格式化后的价格字符串
+     */
+    fun formatPrice(price: Double, currency: String = "CNY"): String {
+        val symbol = when (currency) {
+            "CNY" -> "¥"
+            "USD" -> "$"
+            "EUR" -> "€"
+            else -> currency
+        }
+        
+        return if (price == 0.0) {
+            "免费"
+        } else {
+            "$symbol${String.format("%.2f", price)}"
+        }
+    }
+    
+    /**
+     * 格式化计费周期
+     * @param cycle 计费周期（monthly/yearly）
+     * @return 格式化后的周期字符串
+     */
+    fun formatBillingCycle(cycle: String): String {
+        return when (cycle.lowercase()) {
+            "monthly" -> "/月"
+            "yearly" -> "/年"
+            else -> ""
+        }
+    }
+    
+    /**
+     * 格式化订单状态
+     * @param status 订单状态
+     * @return 格式化后的状态字符串
+     */
+    fun formatOrderStatus(status: String): String {
+        return when (status.lowercase()) {
+            "pending" -> "待支付"
+            "paid" -> "已支付"
+            "failed" -> "支付失败"
+            "cancelled" -> "已取消"
+            else -> status
+        }
+    }
+    
+    /**
+     * 格式化订阅状态
+     * @param status 订阅状态
+     * @return 格式化后的状态字符串
+     */
+    fun formatSubscriptionStatus(status: String): String {
+        return when (status.lowercase()) {
+            "active" -> "有效"
+            "expired" -> "已过期"
+            "cancelled" -> "已取消"
+            else -> status
+        }
+    }
+}

app-android/app/src/main/java/com/huaga/life_echo/utils/TextUtils.kt

@@ -0,0 +1,68 @@
+package com.huaga.life_echo.utils
+
+/**
+ * 文本处理工具
+ */
+object TextUtils {
+    
+    /**
+     * 单行文本省略
+     * @param text 原始文本
+     * @param maxLength 最大长度
+     * @return 省略后的文本
+     */
+    fun ellipsizeSingleLine(text: String?, maxLength: Int = 50): String {
+        if (text.isNullOrBlank()) return ""
+        
+        return if (text.length > maxLength) {
+            text.substring(0, maxLength) + "..."
+        } else {
+            text
+        }
+    }
+    
+    /**
+     * 多行文本省略
+     * @param text 原始文本
+     * @param maxLines 最大行数
+     * @param maxLengthPerLine 每行最大长度
+     * @return 省略后的文本
+     */
+    fun ellipsizeMultiLine(text: String?, maxLines: Int = 3, maxLengthPerLine: Int = 50): String {
+        if (text.isNullOrBlank()) return ""
+        
+        val lines = text.split("\n")
+        if (lines.size <= maxLines) {
+            return text
+        }
+        
+        val result = lines.take(maxLines).joinToString("\n")
+        return if (result.length > maxLines * maxLengthPerLine) {
+            result.substring(0, maxLines * maxLengthPerLine) + "..."
+        } else {
+            result + "..."
+        }
+    }
+    
+    /**
+     * 移除多余的空白字符
+     * @param text 原始文本
+     * @return 处理后的文本
+     */
+    fun trimWhitespace(text: String?): String {
+        return text?.replace(Regex("\\s+"), " ")?.trim() ?: ""
+    }
+    
+    /**
+     * 提取引用内容（以引号包裹的内容）
+     * @param text 原始文本
+     * @return 引用内容列表
+     */
+    fun extractQuotes(text: String?): List<String> {
+        if (text.isNullOrBlank()) return emptyList()
+        
+        // 使用原始字符串避免转义问题
+        val quotePattern = Regex("""["'](.*?)["']""")
+        return quotePattern.findAll(text).map { it.groupValues[1] }.toList()
+    }
+}

app-android/app/src/main/java/com/huaga/life_echo/utils/TimeUtils.kt

@@ -0,0 +1,87 @@
+package com.huaga.life_echo.utils
+
+import java.text.SimpleDateFormat
+import java.util.*
+
+/**
+ * 时间格式化工具
+ */
+object TimeUtils {
+    
+    /**
+     * 格式化时间戳为相对时间
+     * @param timestamp 时间戳（毫秒）
+     * @return 格式化后的时间字符串（刚刚/分钟前/小时前/日期）
+     */
+    fun formatRelativeTime(timestamp: Long?): String {
+        if (timestamp == null) return "刚刚"
+        
+        val now = System.currentTimeMillis()
+        val diff = now - timestamp
+        
+        return when {
+            diff < 60000 -> "刚刚" // 1分钟内
+            diff < 3600000 -> "${diff / 60000}分钟前" // 1小时内
+            diff < 86400000 -> "${diff / 3600000}小时前" // 24小时内
+            diff < 604800000 -> "${diff / 86400000}天前" // 7天内
+            else -> {
+                val date = Date(timestamp)
+                val calendar = Calendar.getInstance()
+                val nowCalendar = Calendar.getInstance()
+                
+                // 如果是今年，显示月日
+                if (calendar.get(Calendar.YEAR) == nowCalendar.get(Calendar.YEAR)) {
+                    SimpleDateFormat("MM月dd日", Locale.getDefault()).format(date)
+                } else {
+                    // 跨年显示年月日
+                    SimpleDateFormat("yyyy年MM月dd日", Locale.getDefault()).format(date)
+                }
+            }
+        }
+    }
+    
+    /**
+     * 格式化时间戳为日期时间
+     * @param timestamp 时间戳（毫秒）
+     * @return 格式化后的日期时间字符串
+     */
+    fun formatDateTime(timestamp: Long?): String {
+        if (timestamp == null) return ""
+        
+        val date = Date(timestamp)
+        val calendar = Calendar.getInstance()
+        val nowCalendar = Calendar.getInstance()
+        calendar.time = date
+        
+        // 判断是否是今天
+        val isToday = calendar.get(Calendar.YEAR) == nowCalendar.get(Calendar.YEAR) &&
+                calendar.get(Calendar.DAY_OF_YEAR) == nowCalendar.get(Calendar.DAY_OF_YEAR)
+        
+        return if (isToday) {
+            "今天 ${SimpleDateFormat("HH:mm", Locale.getDefault()).format(date)}"
+        } else {
+            SimpleDateFormat("MM月dd日 HH:mm", Locale.getDefault()).format(date)
+        }
+    }
+    
+    /**
+     * 格式化更新时间
+     * @param timestamp 时间戳（毫秒）
+     * @return 格式化后的更新时间字符串
+     */
+    fun formatUpdateTime(timestamp: Long?): String {
+        if (timestamp == null) return ""
+        
+        val diff = System.currentTimeMillis() - timestamp
+        return when {
+            diff < 60000 -> "刚刚更新"
+            diff < 3600000 -> "${diff / 60000}分钟前更新"
+            diff < 86400000 -> "${diff / 3600000}小时前更新"
+            diff < 604800000 -> "${diff / 86400000}天前更新"
+            else -> {
+                val date = Date(timestamp)
+                SimpleDateFormat("MM月dd日更新", Locale.getDefault()).format(date)
+            }
+        }
+    }
+}