Add initial setup for local HTTPS debugging and Nginx configuration

- Introduce `setup-certs.sh` script for generating trusted local TLS certificates using mkcert.
- Add Nginx configuration files for local and Docker environments to handle HTTPS requests and proxy to backend services.
- Update `docker-compose.yaml` to include Nginx service for unified TLS entry and adjust frontend service ports for local development.
- Create `AGENTS.md` and `README.md` files to document the local HTTPS setup process and usage instructions.
- Modify backend startup commands in `README.md` for consistency with new requirements.
- Add `.gitignore` to exclude generated certificates from version control.

backend/app.py

@@ -1,6 +1,6 @@
 """FastAPI 入口。挂载路由,放行前端跨域,启动时建表。
 
-启动:  uvicorn app:app --reload --port 8000
+启动:  uv run --with-requirements requirements.txt uvicorn app:app --reload --port 8000
 
 路由分组(对齐 dograh 的 routes/ 结构):
   /health              健康检查