refactor(api,expo): 多智能体与会话收敛、回忆录兼容层移除、后端测试集大幅删减

- 对齐「多智能体收敛」与「回忆录 stories-first / markdown-first」方向：收紧运行时契约、
  删除过渡兼容路径与双轨逻辑，并同步更新客户端与文档。

- Chat：以 ChatOrchestrator 为实时编排入口；删除独立 conversation_agent，精简 prompts。
- Memoir：删除 memory_agent；MemoirOrchestrator、classification / story_route 与 prompts 收敛到
  prepare_batches + run_story_pipeline_for_category_batch 主链路。
- 将 agents 侧 processor 迁入 feature 层为 background_runner，并移除 features 下重复/过时
  processor 封装。

- 新增 history_store，强化「conversation_messages 为 DB 真源、Redis 为缓存」模型。
- 调整 models、repo、service、session_history；精简 WS message_types，重构 pipeline 与 router。

- 移除章节占位、整章再生等旧路径；章节列表与封面逻辑要求 story 关联；收紧 cover 资格与
  enqueue。
- helpers、repo、service、router、reading_segment_materialize、story_pipeline_sync、pdf_service
  等按 canonical markdown / cover_asset_id 收缩；删除 memoir_images/provider 等冗余。
- tasks：memoir_tasks、chapter_cover_tasks 等大幅瘦身；story_image_tasks 等与当前图片任务对齐。

- core：config、logging、redis、task_tracker 小幅调整。
- auth / user / payment / quota：路由或服务侧删减过时接口或逻辑（如 payment router 行数减少）。

- pyproject.toml、development.sh、.env.example / .env.production、README 等同步说明或变量。

- Alembic 0001_initial_schema 微调（与当前 schema 叙事一致的小改动）。

- 回忆录：types / mappers / api、章节页与 memoir 页与后端契约对齐；markdown-renderer 调整。
- 语音：删除 voice/player，voice-segment-store 相应精简。

- api/tests：删除 conftest 及绝大部分既有测试文件（websocket_baseline、conversation、memoir
  图片、PDF、SMS 等），属有意收缩/待按 backend-test-system 重建的信号。
- docs：新增多智能体收敛与移除兼容层计划摘要；更新 story-first 设计、backend-test-system、
  multi-agent-refactor-plan、实施总结等。

BREAKING CHANGE: 后端对外契约、回忆录章节字段与若干路由/任务行为已变更；大量 API 测试被移除，
  CI 若依赖这些用例需按新策略补测或调整流水线。

app-expo/src/i18n/generated/resources.ts

@@ -99,6 +99,10 @@ interface Resources {
   };
   explore: {};
   home: {};
+  legal: {
+    titlePrivacy: 'Privacy Policy';
+    titleTerms: 'User Agreement';
+  };
   memoir: {
     chapterLabel: 'Chapter {{index}}';
     chapterReading: {
@@ -125,6 +129,18 @@ interface Resources {
     continueWriting: 'Continue Writing';
     emptySubtitle: 'Chat with Echo to record your stories';
     emptyTitle: 'No memoir yet';
+    frameworkChapters: {
+      chapter1: 'Childhood and upbringing';
+      chapter2: 'Education and young adulthood';
+      chapter3: 'Early career';
+      chapter4: 'Major achievements and peak moments';
+      chapter5: 'Setbacks, challenges, and turning points';
+      chapter6: 'Family and relationships';
+      chapter7: 'Beliefs and values';
+      chapter8: 'Life summary';
+    };
+    loadErrorMessage: 'Could not load chapters';
+    loadErrorRetry: 'Retry';
     pageTitle: 'Memoir';
     readMemory: 'Read Memory';
     startChapter: 'Start Writing';

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

@@ -0,0 +1,4 @@
+{
+  "titleTerms": "User Agreement",
+  "titlePrivacy": "Privacy Policy"
+}

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

@@ -1,4 +1,16 @@
 {
+  "frameworkChapters": {
+    "chapter1": "Childhood and upbringing",
+    "chapter2": "Education and young adulthood",
+    "chapter3": "Early career",
+    "chapter4": "Major achievements and peak moments",
+    "chapter5": "Setbacks, challenges, and turning points",
+    "chapter6": "Family and relationships",
+    "chapter7": "Beliefs and values",
+    "chapter8": "Life summary"
+  },
+  "loadErrorMessage": "Could not load chapters",
+  "loadErrorRetry": "Retry",
   "chapterLabel": "Chapter {{index}}",
   "chapterReading": {
     "back": "Back",

app-expo/src/i18n/locales/zh/legal.json

@@ -0,0 +1,4 @@
+{
+  "titleTerms": "用户协议",
+  "titlePrivacy": "隐私政策"
+}

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

@@ -1,4 +1,16 @@
 {
+  "frameworkChapters": {
+    "chapter1": "童年与成长背景",
+    "chapter2": "教育经历与青年时期",
+    "chapter3": "崭露头角",
+    "chapter4": "主要成就与巅峰时刻",
+    "chapter5": "挫折、挑战与重大转折",
+    "chapter6": "家庭与情感",
+    "chapter7": "信念与价值观",
+    "chapter8": "人生总结"
+  },
+  "loadErrorMessage": "无法加载章节列表",
+  "loadErrorRetry": "重试",
   "chapterLabel": "第 {{index}} 章",
   "chapterReading": {
     "back": "返回",

app-expo/src/i18n/resources/index.ts

@@ -4,6 +4,7 @@ import commonEn from '../locales/en/common.json';
 import conversationEn from '../locales/en/conversation.json';
 import exploreEn from '../locales/en/explore.json';
 import homeEn from '../locales/en/home.json';
+import legalEn from '../locales/en/legal.json';
 import memoirEn from '../locales/en/memoir.json';
 import profileEn from '../locales/en/profile.json';
 import appZh from '../locales/zh/app.json';
@@ -12,6 +13,7 @@ import commonZh from '../locales/zh/common.json';
 import conversationZh from '../locales/zh/conversation.json';
 import exploreZh from '../locales/zh/explore.json';
 import homeZh from '../locales/zh/home.json';
+import legalZh from '../locales/zh/legal.json';
 import memoirZh from '../locales/zh/memoir.json';
 import profileZh from '../locales/zh/profile.json';
 
@@ -28,6 +30,7 @@ export const namespaces = [
   'conversation',
   'home',
   'explore',
+  'legal',
   'memoir',
   'profile',
 ] as const;
@@ -42,6 +45,7 @@ export const resources = {
     conversation: conversationZh,
     home: homeZh,
     explore: exploreZh,
+    legal: legalZh,
     memoir: memoirZh,
     profile: profileZh,
   },
@@ -52,6 +56,7 @@ export const resources = {
     conversation: conversationEn,
     home: homeEn,
     explore: exploreEn,
+    legal: legalEn,
     memoir: memoirEn,
     profile: profileEn,
   },