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/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",