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/tests/test_dao.py

@@ -0,0 +1,85 @@
+import os
+import pytest
+
+os.environ["DB_TYPE"] = "sqlite"
+os.environ["DB_PATH"] = ":memory:"
+
+
+def test_sqlite_connection():
+    """Test SQLite database works."""
+    from sqlalchemy import create_engine, text
+    from app.models import Base
+
+    engine = create_engine("sqlite:///:memory:", echo=False)
+    Base.metadata.create_all(bind=engine)
+
+    with engine.connect() as conn:
+        conn.execute(text("INSERT INTO parents (openid, nickname, status) VALUES ('test', 'Test', 1)"))
+        conn.commit()
+        result = conn.execute(text("SELECT * FROM parents")).fetchall()
+        assert len(result) == 1
+
+
+def test_parent_dao():
+    """Test ParentDAO."""
+    from sqlalchemy import create_engine
+    from sqlalchemy.orm import sessionmaker
+    from app.models import Base
+    from app.dao.parent import ParentDAO
+
+    engine = create_engine("sqlite:///:memory:", echo=False)
+    Base.metadata.create_all(bind=engine)
+    Session = sessionmaker(bind=engine)
+    db = Session()
+
+    dao = ParentDAO(db)
+    user_id = dao.create("test_openid", None, "Test User")
+    assert user_id > 0
+
+    parent = dao.get_by_id(user_id)
+    assert parent["openid"] == "test_openid"
+
+
+def test_child_dao():
+    """Test ChildDAO."""
+    from sqlalchemy import create_engine
+    from sqlalchemy.orm import sessionmaker
+    from app.models import Base
+    from app.dao.child import ChildDAO
+
+    engine = create_engine("sqlite:///:memory:", echo=False)
+    Base.metadata.create_all(bind=engine)
+    Session = sessionmaker(bind=engine)
+    db = Session()
+
+    dao = ChildDAO(db)
+    child_id = dao.create(1, "Test Child")
+    assert child_id > 0
+
+    child = dao.get_by_id(child_id)
+    assert child["child_name"] == "Test Child"
+
+
+def test_binding_dao():
+    """Test BindingDAO."""
+    from sqlalchemy import create_engine
+    from sqlalchemy.orm import sessionmaker
+    from app.models import Base
+    from app.dao.binding import BindingDAO
+
+    engine = create_engine("sqlite:///:memory:", echo=False)
+    Base.metadata.create_all(bind=engine)
+    Session = sessionmaker(bind=engine)
+    db = Session()
+
+    dao = BindingDAO(db)
+    token = dao.start_bind(1, "device_123", 1)
+    assert len(token) == 36
+
+
+if __name__ == "__main__":
+    test_sqlite_connection()
+    test_parent_dao()
+    test_child_dao()
+    test_binding_dao()
+    print("All DAO tests passed!")