首个可运行的版本

backend/app/models/__init__.py

@@ -0,0 +1,19 @@
+"""SQLAlchemy 模型包 - 导入所有模型供 Alembic 自动检测"""
+
+from app.models.user import User
+from app.models.conversation import Conversation
+from app.models.conversation_member import ConversationMember
+from app.models.message import Message
+from app.models.friend import Friend
+from app.models.friend_request import FriendRequest
+from app.models.system_config import SystemConfig
+
+__all__ = [
+    "User",
+    "Conversation",
+    "ConversationMember",
+    "Message",
+    "Friend",
+    "FriendRequest",
+    "SystemConfig",
+]