first add

backend/app/models/base.py

@@ -0,0 +1,25 @@
+"""基础模型"""
+from datetime import datetime
+from sqlmodel import SQLModel, Field
+from uuid import uuid4
+
+
+def generate_uuid() -> str:
+    """生成 UUID"""
+    return str(uuid4())
+
+
+class TimestampModel(SQLModel):
+    """时间戳 Mixin"""
+    created_at: datetime = Field(
+        default_factory=datetime.utcnow,
+        nullable=False,
+        sa_column_kwargs={"index": True},
+    )
+    updated_at: datetime = Field(
+        default_factory=datetime.utcnow,
+        nullable=False,
+        sa_column_kwargs={"onupdate": datetime.utcnow},
+    )
+
+