Add brain memory services and APIs

Introduce the backend pieces for brain memory ingestion, routing, and
system telemetry so the new knowledge workflows can project data into a
brain view. The supporting tests lock in the new behavior and keep the
expanded backend surface stable.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/README.md

@@ -19,12 +19,12 @@ cp .env.example .env
 ### 3. 启动开发服务器
 
 ```bash
-uv run uvicorn app.main:app --reload --port 8000
+uv run uvicorn app.main:app --reload --host 127.0.0.1 --port 9527
 ```
 
 ### 4. API 文档
 
-启动后访问 http://localhost:8000/docs 查看交互式 API 文档。
+启动后访问 http://localhost:9527/docs 查看交互式 API 文档。
 
 ## 环境变量