feat(api): add database models

api/app/models/user.py

@@ -0,0 +1,14 @@
+from sqlalchemy import Column, Integer, String, DateTime
+from sqlalchemy.sql import func
+
+from app.database import Base
+
+
+class AdminUser(Base):
+    """管理员用户表模型"""
+    __tablename__ = "admin_users"
+
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    username = Column(String(50), unique=True, nullable=False)
+    password_hash = Column(String(255), nullable=False)
+    created_at = Column(DateTime, default=func.now())