Implement Alembic for database migrations and update FastAPI initialization

- Integrate Alembic for managing database schema migrations, replacing the previous SQL schema management.
- Update the FastAPI application to synchronize interface definitions at startup.
- Modify the Docker Compose command to run Alembic migrations before starting the API.
- Enhance the Makefile with new commands for database migration and revision management.
- Remove outdated SQL schema and seed files, transitioning to a more dynamic migration approach.
- Add initial migration scripts and configuration for Alembic, ensuring a structured database evolution.

docker-compose.yaml

@@ -36,7 +36,7 @@ services:
   api:
     build: ./backend
     # 调试:挂源码 + --reload,改代码即时生效,无需重建镜像
-    command: uvicorn app:app --host 0.0.0.0 --port 8000 --reload
+    command: sh -c "alembic upgrade head && uvicorn app:app --host 0.0.0.0 --port 8000 --reload"
     volumes:
       - ./backend:/app
       - /app/.venv          # 屏蔽宿主机的 venv(容器用镜像内的依赖)