feat(memory,conversation): 记忆富化/证据包、时间线幂等字段与对话分段全链路

数据库
- 新增迁移 0003：timeline_events.memory_source_id 外键 → memory_sources，便于按 ingest 源做时间线幂等

后端 - 记忆
- 新增 ingest 后 LLM 富化（摘要/事实/时间线），可配置开关与最大字符数
- 新增证据包组装：合并 chunk、摘要、事实、时间线、故事等检索结果；支持空 query 时是否仍带 rolling 等开关
- repo/retriever/service/router/schemas/summarizer/timeline/extractor 等扩展；文档 memory-retrieval.md 更新

后端 - 对话 WS
- 增加 PING/PONG；分段 ASR 日志与空音频处理；转写失败与「无助手回复」错误提示更明确
- 助手多段回复持久化使用统一分隔符，与分段逻辑一致

后端 - Agent
- reply_limits：按 [SPLIT] 与段落拆段，并保证非空 fallback，供 WS 与 TTS 多段下发

后端 - 回忆录任务
- transcript ingest 记录 source_id；任务成功结?

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

@@ -28,7 +28,7 @@
     "purgeOpenConfirm": "I understand, continue",
     "purgePhraseHint": "Type the following Chinese sentence exactly (every character and punctuation). The server only accepts this exact phrase:",
     "purgeSubmitting": "Deleting…",
-    "purgeWarningBody": "This permanently deletes your conversations, memory, stories, chapters, orders, and related files in cloud storage. All devices will be signed out.\nYou can still log in with the same phone number, but your previous content cannot be restored.",
+    "purgeWarningBody": "This permanently deletes your conversations, memory, stories, chapters, orders, and related files in cloud storage. Profile fields such as birth year, birthplace, where you grew up, and occupation will also be cleared. All devices will be signed out.\nYou can still log in with the same phone number, but your previous content cannot be restored.",
     "purgeWarningTitle": "Before you continue",
     "title": "Data & Privacy"
   },