fix: 头像缓存版本号；移除回忆录撰写入口跳转聊天

- API：上传/预设头像 URL 追加 ?v=time.time_ns()，避免同路径缓存导致「只能换一次头像」
- Expo：回忆录 Tab 去掉撰写中「继续写作」及新建会话跳转；清理 memoir 文案键并更新 i18n 类型

未纳入提交：本地 api/uploads/（开发环境头像文件）

Co-authored-by: Cursor <cursoragent@cursor.com>

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

@@ -33,12 +33,10 @@
     "settings": "Settings",
     "typography": "Typography"
   },
-  "continueWriting": "Continue Writing",
   "emptySubtitle": "Chat with your companion to record your stories",
   "emptyTitle": "No memoir yet",
   "pageTitle": "Memoir",
   "readMemory": "Read Memory",
-  "startChapter": "Start Writing",
   "statusDrafting": "Drafting",
   "statusLocked": "Locked",
   "statusPending": "Pending",