feat(api+app): 对话阶段化、回忆录流水线与客户端会话体验

- DB: segments 用户输入文本（Alembic 0002）
- Chat: 阶段检测/阶段提示/回复限制，编排与访谈/画像 prompts 调整
- Memoir: 忠实度检查 agent，叙事与分类等链路更新
- Core: agent 日志、Alembic 启动、LangChain/日志/配置等
- Story: time_hints；Memory 检索与相关测试
- Expo: 助手头像、会话页与消息拆分、实时会话与文案/i18n
- Docs/scripts/tests: 迁移脚本、LLM JSON/记忆检索文档、新增单测

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

@@ -4,6 +4,7 @@
   "chatUnavailableTitle": "Chat unavailable",
   "chatUnavailableConnecting": "Reconnecting now. You can keep typing and send once the connection is back.",
   "chatUnavailableDisconnected": "Connection lost. You can keep typing and send after reconnecting.",
+  "chatQueueSendTimeout": "Connection timed out. Check your network and try again.",
   "confirm": "OK",
   "cancel": "Cancel",
   "delete": "Delete",
@@ -15,7 +16,7 @@
   "connectionConnected": "Connected",
   "connectionConnecting": "Connecting...",
   "connectionDisconnected": "Disconnected",
-  "emptyGreetingSubtitle": "Chat with Echo and record your stories.",
+  "emptyGreetingSubtitle": "Chat with your companion and record your stories.",
   "greetingTitle": "Say Hello",
   "inputPlaceholder": "Type a message...",
   "inputPlaceholderVoice": "Type here or hold the mic to speak...",
@@ -23,7 +24,7 @@
   "recentChats": "Recent Chats",
   "recordingPermissionDenied": "Microphone permission is required to record",
   "send": "Send",
-  "startNewSubtitle": "Capture a new memory or share your thoughts with Echo.",
+  "startNewSubtitle": "Capture a new memory or share your thoughts with your companion.",
   "switchToText": "Switch to text input",
   "switchToVoice": "Switch to voice input",
   "tapToEndRecording": "Tap to end",

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

@@ -34,7 +34,7 @@
     "typography": "Typography"
   },
   "continueWriting": "Continue Writing",
-  "emptySubtitle": "Chat with Echo to record your stories",
+  "emptySubtitle": "Chat with your companion to record your stories",
   "emptyTitle": "No memoir yet",
   "pageTitle": "Memoir",
   "readMemory": "Read Memory",