feat: 章节软删除、对话左滑删除，移除已读状态

- 章节：详情页增加删除按钮，软删除（is_active=False），AI 不再修改但保留供参考
- 章节：get_chapter 增加 is_active 校验，已删除章节返回 404
- 章节：AI 生成时参考同类别已删除章节摘要
- 对话：左滑显示删除，调用 hard delete API，删除前二次确认
- 对话：根布局包裹 GestureHandlerRootView 以支持 Swipeable
- 对话：移除已读/未读状态展示及相关 i18n

app-expo/src/i18n/locales/en/conversation.json

@@ -1,6 +1,10 @@
 {
+  "confirmDeleteConversation": "Are you sure you want to delete this conversation? It cannot be recovered.",
   "createError": "Unable to create conversation. Please check your network and try again.",
   "confirm": "OK",
+  "cancel": "Cancel",
+  "delete": "Delete",
+  "deleteConversation": "Delete Conversation",
   "addMore": "More",
   "agentName": "Life Echo",
   "cancelRecording": "Cancel recording",
@@ -13,7 +17,6 @@
   "inputPlaceholder": "Type a message...",
   "inputPlaceholderVoice": "Type here or hold the mic to speak...",
   "me": "Me",
-  "read": "Read",
   "recentChats": "Recent Chats",
   "recordingPermissionDenied": "Microphone permission is required to record",
   "send": "Send",
@@ -22,7 +25,6 @@
   "switchToVoice": "Switch to voice input",
   "tapToEndRecording": "Tap to end",
   "tapToStartRecording": "Tap to start recording",
-  "unread": "Unread",
   "viewAll": "View All",
   "voiceMessagePreview": "Voice message"
 }

app-expo/src/i18n/locales/en/memoir.json

@@ -2,6 +2,10 @@
   "chapterLabel": "Chapter {{index}}",
   "chapterReading": {
     "back": "Back",
+    "cancel": "Cancel",
+    "confirmDeleteMessage": "Are you sure you want to delete this chapter? You will no longer be able to view it, but the content will be kept for future reference.",
+    "deleteChapter": "Delete Chapter",
+    "deleteChapterAction": "Delete",
     "backgroundColor": "Background",
     "bgPureWhite": "White",
     "bgSepia": "Sepia",