feat: mongodb 单后端精简分支 — Beanie 2.x + pymongo async，移除 MySQL/alembic

docker-compose.yml

@@ -5,23 +5,10 @@ services:
       - "8000:8000"
     env_file: .env
     environment:
-      # compose 内网地址覆盖 .env 里的 127.0.0.1
-      MYSQL_DSN: mysql+aiomysql://root:root@mysql:3306/app?charset=utf8mb4
       MONGO_DSN: mongodb://mongo:27017
     depends_on:
-      - mysql
       - mongo
 
-  mysql:
-    image: mysql:8.0
-    environment:
-      MYSQL_ROOT_PASSWORD: root
-      MYSQL_DATABASE: app
-    ports:
-      - "3306:3306"
-    volumes:
-      - mysql_data:/var/lib/mysql
-
   mongo:
     image: mongo:8.0
     ports:
@@ -30,5 +17,4 @@ services:
       - mongo_data:/data/db
 
 volumes:
-  mysql_data:
   mongo_data: