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/settings.py

@@ -1,4 +1,5 @@
 from functools import lru_cache
+from pathlib import Path
 from urllib.parse import quote_plus
 
 from pydantic import Field
@@ -21,11 +22,13 @@ class Settings(BaseSettings):
     host: str = Field(default="0.0.0.0", validation_alias="HOST")
     port: int = Field(default=8001, validation_alias="PORT")
 
+    db_type: str = Field(default="mysql", validation_alias="DB_TYPE")
     db_host: str = Field(default="127.0.0.1", validation_alias="DB_HOST")
     db_port: int = Field(default=3306, validation_alias="DB_PORT")
     db_user: str = Field(default="root", validation_alias="DB_USER")
     db_password: str = Field(default="", validation_alias="DB_PASSWORD")
     db_name: str = Field(default="mini_program", validation_alias="DB_NAME")
+    db_path: str = Field(default="./data.db", validation_alias="DB_PATH")
     jwt_secret: str = Field(
         default="dev_only_change_jwt_secret",
         validation_alias="JWT_SECRET",
@@ -49,6 +52,18 @@ class Settings(BaseSettings):
             f"{self.db_name}?charset=utf8mb4"
         )
 
+    @property
+    def sqlite_dsn(self) -> str:
+        db_path = Path(self.db_path)
+        db_path.parent.mkdir(parents=True, exist_ok=True)
+        return f"sqlite:///{db_path.absolute()}"
+
+    @property
+    def database_dsn(self) -> str:
+        if self.db_type == "sqlite":
+            return self.sqlite_dsn
+        return self.mysql_dsn
+
 
 @lru_cache(maxsize=1)
 def get_settings() -> Settings: