新增小程序后端代码，包括数据库、路由、服务层等。

小程序前后端打通，包括登录、注册、绑定设备、查询绑定信息，修改小朋友名称等功能。

mini-program/app/main.py

@@ -5,23 +5,30 @@ from fastapi import FastAPI
 
 try:
     # For module mode: `uvicorn app.main:app`
-    from app.db import check_db_connection, close_db_engine
+    from app.db import check_db_connection, close_db_engine, init_db_tables
     from app.logging_setup import configure_logging
     from app.middleware.auth import install_auth_middleware
     from app.middleware.request_log import install_request_logging_middleware
     from app.routers.auth import router as auth_router
+    from app.routers.wechat_auth import router as wechat_auth_router
     from app.routers.health import router as health_router
     from app.routers.messages import router as messages_router
+    from app.routers.parents import router as parents_router
+    from app.routers.children import router as children_router
+    from app.routers.bindings import router as bindings_router
     from app.settings import settings
 except ModuleNotFoundError:
     # For script mode: `python app/main.py` or VS Code "Run Python File"
-    from db import check_db_connection, close_db_engine
+    from db import check_db_connection, close_db_engine, init_db_tables
     from logging_setup import configure_logging
     from middleware.auth import install_auth_middleware
     from middleware.request_log import install_request_logging_middleware
     from routers.auth import router as auth_router
     from routers.health import router as health_router
     from routers.messages import router as messages_router
+    from routers.parents import router as parents_router
+    from routers.children import router as children_router
+    from routers.bindings import router as bindings_router
     from settings import settings
 
 
@@ -39,6 +46,7 @@ def create_app() -> FastAPI:
     @app.on_event("startup")
     def on_startup() -> None:
         check_db_connection()
+        init_db_tables()
         logger.info("application started", extra={"event": "app_start"})
 
     @app.on_event("shutdown")
@@ -48,9 +56,15 @@ def create_app() -> FastAPI:
 
     install_auth_middleware(app)
     install_request_logging_middleware(app)
-    app.include_router(auth_router)
+    app.include_router(wechat_auth_router)
     app.include_router(health_router)
     app.include_router(messages_router)
+    try:
+        app.include_router(parents_router)
+        app.include_router(children_router)
+        app.include_router(bindings_router)
+    except NameError:
+        pass
     return app