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/models/schemas/widget_app.py

@@ -0,0 +1,67 @@
+"""
+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 pydantic import BaseModel, Field
+from typing import Optional
+from uuid import UUID
+from datetime import datetime
+
+
+class WidgetAppBase(BaseModel):
+    """Base schema with common fields"""
+    name: str = Field(..., min_length=1, max_length=100, description="App name (e.g., 'Production Widget')")
+    description: Optional[str] = Field(None, max_length=500, description="Optional description")
+
+
+class WidgetAppCreate(WidgetAppBase):
+    """Schema for creating a new widget app"""
+    pass
+
+
+class WidgetAppUpdate(BaseModel):
+    """Schema for updating widget app"""
+    name: Optional[str] = Field(None, min_length=1, max_length=100)
+    description: Optional[str] = None
+    is_active: Optional[bool] = None
+
+
+class WidgetAppResponse(WidgetAppBase):
+    """Schema for widget app response (without API key)"""
+    id: UUID
+    organization_id: UUID
+    created_by: UUID
+    is_active: bool
+    created_at: datetime
+    updated_at: datetime
+
+    class Config:
+        from_attributes = True
+
+
+class WidgetAppWithKeyResponse(WidgetAppResponse):
+    """
+    Schema for newly created app (includes API key ONCE).
+
+    IMPORTANT: Only use this for create/regenerate responses.
+    Never log or persist the api_key field.
+    """
+    api_key: str = Field(..., description="API key - SAVE THIS! It won't be shown again.")
+
+
+class WidgetAppListResponse(BaseModel):
+    """Schema for list of widget apps"""
+    total: int
+    apps: list[WidgetAppResponse]