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/features/voice/player.ts

@@ -1,9 +0,0 @@
-/**
- * Player is now fully implemented in hooks/use-player.ts as a self-contained
- * React hook. expo-audio's hook-centric API (useAudioPlayer + useAudioPlayerStatus)
- * makes a class-level player impractical — completion detection, source replacement,
- * and lifecycle management all need React context.
- *
- * This file re-exports the hook for backward compatibility with any imports.
- */
-export { usePlayer } from './hooks/use-player';

app-expo/src/features/voice/voice-segment-store.ts

@@ -18,21 +18,6 @@ const CREATE_TABLE_SQL = `
 
 let initialized = false;
 
-async function migrateLegacyVoiceMessageLocal(): Promise<void> {
-  const rows = await querySql<{ name: string }>(
-    `SELECT name FROM sqlite_master WHERE type='table' AND name='voice_message_local'`,
-  );
-  if (rows.length === 0) return;
-  const now = Date.now();
-  await executeSql(
-    `INSERT OR IGNORE INTO segment_outbox (conversation_id, voice_session_id, segment_index, file_uri, duration_ms, status, retry_count, created_at)
-     SELECT conversation_id, voice_session_id, 0, file_uri, duration_ms, 'sent', 0, ?
-     FROM voice_message_local`,
-    [now],
-  );
-  await executeSql(`DROP TABLE IF EXISTS voice_message_local`);
-}
-
 async function ensureTable(): Promise<void> {
   if (initialized) return;
   await executeSql(CREATE_TABLE_SQL);
@@ -40,7 +25,6 @@ async function ensureTable(): Promise<void> {
     `CREATE UNIQUE INDEX IF NOT EXISTS uq_segment_outbox_voice_session_segment
      ON segment_outbox(voice_session_id, segment_index)`,
   );
-  await migrateLegacyVoiceMessageLocal();
   initialized = true;
 }
 
@@ -192,6 +176,3 @@ export const voiceSegmentStore = {
     initialized = false;
   },
 } as const;
-
-/** @deprecated 使用 voiceSegmentStore */
-export const segmentOutbox = voiceSegmentStore;