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/db.py

@@ -13,14 +13,34 @@ except ModuleNotFoundError:
     from settings import settings
 
 
-engine = create_engine(
-    settings.mysql_dsn,
-    pool_size=5,
-    max_overflow=10,
-    pool_pre_ping=True,
-    pool_recycle=1800,
-    future=True,
-)
+def _create_engine() -> create_engine:
+    if settings.db_type == "sqlite":
+        return create_engine(
+            settings.sqlite_dsn,
+            connect_args={"check_same_thread": False},
+            future=True,
+        )
+    return create_engine(
+        settings.mysql_dsn,
+        pool_size=5,
+        max_overflow=10,
+        pool_pre_ping=True,
+        pool_recycle=1800,
+        future=True,
+    )
+
+
+engine = _create_engine()
+
+
+@event.listens_for(engine, "connect")
+def set_sqlite_pragma(dbapi_conn, connection_record):
+    if settings.db_type == "sqlite":
+        cursor = dbapi_conn.cursor()
+        cursor.execute("PRAGMA foreign_keys=ON")
+        cursor.close()
+
+
 logger = logging.getLogger("app.db")
 
 
@@ -79,6 +99,13 @@ def get_db() -> Generator[Session, None, None]:
         db.close()
 
 
+def init_db_tables() -> None:
+    from app.models import Base
+
+    Base.metadata.create_all(bind=engine)
+    logger.info("database tables initialized", extra={"event": "db_init"})
+
+
 def check_db_connection() -> None:
     with engine.connect() as conn:
         conn.execute(text("SELECT 1"))