docs: add data source flow guide and localize handoff READMEs

- Add docs/DATA_SOURCE_FLOW.md: end-to-end source -> NotebookLM ->
  storage -> App flow, source list with publish frequency, institution
  intro status, ingestion artifact structure, and known cadence gaps
- Link the new doc from README and PROJECT_OVERVIEW indexes
- Localize top-level and subproject READMEs to Chinese for handoff
  (pre-existing working-tree changes)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -1,54 +1,54 @@
 # report-notebooklm-app
 
-Flutter client for the report-notebooklm Phase 1 app shell.
+report-notebooklm 第一阶段应用外壳的 Flutter 客户端。
 
-The backend API lives in `../report-notebooklm-api/` in the same monorepo. API/data/content-pipeline details are documented there; this directory focuses on App handoff, UI state, build commands, and integration notes.
+后端 API 在同一个 monorepo 的 `../report-notebooklm-api/` 里。API、数据、内容流水线的细节都记在那边；这个目录专注于应用交接、UI 状态、构建命令和对接说明。
 
-## Read First
+## 先读这些
 
-- [docs/HANDOFF.md](docs/HANDOFF.md): current App state, implemented screens, placeholders, and next work.
-- [docs/PROJECT_BRIEF.md](docs/PROJECT_BRIEF.md): product and Phase 1 scope snapshot.
-- [docs/APP_RUNBOOK.md](docs/APP_RUNBOOK.md): Flutter version, local run, web build, Android debug build, and verification.
-- [docs/API_CONTRACT_NOTES.md](docs/API_CONTRACT_NOTES.md): endpoints and fields consumed by the App.
-- [docs/PROJECT_MAP.md](docs/PROJECT_MAP.md): source tree map.
+- [docs/HANDOFF.md](docs/HANDOFF.md)：当前应用状态、已实现的页面、占位项，以及下一步工作。
+- [docs/PROJECT_BRIEF.md](docs/PROJECT_BRIEF.md)：产品和第一阶段范围速览。
+- [docs/APP_RUNBOOK.md](docs/APP_RUNBOOK.md)：Flutter 版本、本地运行、Web 构建、Android 调试构建和验证。
+- [docs/API_CONTRACT_NOTES.md](docs/API_CONTRACT_NOTES.md)：应用所消费的接口和字段。
+- [docs/PROJECT_MAP.md](docs/PROJECT_MAP.md)：源码目录地图。
 
-## Product Boundary
+## 产品边界
 
-This repo contains App code and an engineering handoff snapshot. It is not the product source of truth.
+这个仓库装的是应用代码和一份工程交接快照，不是产品的唯一真源。
 
-Product SSOT: mall-docs report-notebooklm docs. Snapshot date: 2026-06-03.
+产品 SSOT：mall-docs 里的 report-notebooklm 文档。快照日期：2026-06-03。
 
-Use `report-notebooklm` and `rnb` for technical identifiers. The user-facing product name is `研听`.
+技术标识符用 `report-notebooklm` 和 `rnb`，面向用户的产品名是 `研听`。
 
-## Requirements
+## 环境要求
 
-- Flutter 3.44.1 / Dart 3.12.1 or compatible newer versions.
-- A running backend that serves `/api/report-notebooklm/v1`.
-- For Android builds: Android SDK, accepted licenses, and an emulator or device.
+- Flutter 3.44.1 / Dart 3.12.1，或兼容的更新版本。
+- 一个正在运行、提供 `/api/report-notebooklm/v1` 的后端。
+- 做 Android 构建还需要：Android SDK、已接受的许可协议，以及一台模拟器或真机。
 
-## API Base URL
+## API 基础地址
 
-The App intentionally has no built-in live API default. Pass the backend base URL explicitly:
+应用刻意不内置任何线上 API 默认值。请显式传入后端基础地址：
 
 ```bash
 flutter run -d chrome --dart-define=RNB_API_BASE=<api-base-url>
 ```
 
-Android emulator:
+Android 模拟器：
 
 ```bash
 flutter run -d <emulator-id> --dart-define=RNB_API_BASE=<emulator-api-base-url>
 ```
 
-Same-network Android device:
+同一局域网内的 Android 真机：
 
 ```bash
 flutter run -d <device-id> --dart-define=RNB_API_BASE=http://<host-lan-ip>:<port>/api/report-notebooklm/v1
 ```
 
-Only use cleartext HTTP for debug builds. Release builds must use HTTPS.
+明文 HTTP 只能用于调试构建。发布构建必须使用 HTTPS。
 
-## Verify
+## 验证
 
 ```bash
 flutter analyze
@@ -57,21 +57,21 @@ flutter build web --dart-define=RNB_API_BASE=<api-base-url>
 flutter build apk --debug --dart-define=RNB_API_BASE=<emulator-api-base-url>
 ```
 
-## Current App Scope
+## 当前应用范围
 
-Implemented:
+已实现：
 
-- Five bottom tabs: 推荐, 研报, 机构, 听单, 我的.
-- API-backed feed, report list, institution list, listen list, institution detail, and report detail.
-- Module renderer registry for inline and card-plus-page modules.
-- Product display name `研听`.
-- Local UI placeholders for login, favorite, outbound confirmation, and playback progress.
+- 五个底部标签页：推荐、研报、机构、听单、我的。
+- 基于 API 的信息流、研报列表、机构列表、听单、机构详情和研报详情。
+- 用于内联模块和「卡片 + 页面」模块的模块渲染器注册表。
+- 产品显示名 `研听`。
+- 登录、收藏、外链跳转确认、播放进度的本地 UI 占位。
 
-Not implemented yet:
+尚未实现：
 
-- Real auth.
-- Real favorite/history/saved-listen sync.
-- Real playable audio stream.
-- Real outbound event write.
-- Production API domain.
-- Release signing, final icon, and final store metadata.
+- 真实鉴权。
+- 真实的收藏 / 历史 / 收听记录同步。
+- 真正可播放的音频流。
+- 真实的外链事件写入。
+- 生产 API 域名。
+- 发布签名、最终图标和最终应用商店元信息。