feat(models): 组织、用户、角色、客户、会话与消息模型

按组织边界定义数据关系，补齐仓储层与通用工具，迁移脚本可重复执行。

backend/app/repositories/widget.py

@@ -0,0 +1,60 @@
+"""
+Copyright 2024-2026 ChatterMate
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+"""
+
+from sqlalchemy.orm import Session
+from app.models.widget import Widget
+from app.models.schemas.widget import WidgetCreate
+
+class WidgetRepository:
+    def __init__(self, db: Session):
+        self.db = db
+
+    def create_widget(self, widget: WidgetCreate, organization_id: str) -> Widget:
+        db_widget = Widget(
+            name=widget.name,
+            organization_id=organization_id,
+            agent_id=widget.agent_id
+        )
+        self.db.add(db_widget)
+        self.db.commit()
+        self.db.refresh(db_widget)
+        return db_widget
+
+
+    def get_widget(self, widget_id: str) -> Widget:
+        return self.db.query(Widget).filter(Widget.id == widget_id).first()
+
+
+    def get_widgets(self, organization_id: str) -> list[Widget]:
+        return self.db.query(Widget).filter(Widget.organization_id == organization_id).all()
+
+
+    def get_widgets_by_agent(self, agent_id: str) -> list[Widget]:
+        """
+        Get all widgets associated with a specific agent.
+        
+        Args:
+            agent_id: The ID of the agent
+            
+        Returns:
+            List of Widget objects associated with the agent
+        """
+        return self.db.query(Widget).filter(Widget.agent_id == agent_id).all()
+
+
+    def delete_widget(self, widget_id: str) -> None:
+        self.db.query(Widget).filter(Widget.id == widget_id).delete()
+        self.db.commit()