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/organization.py

@@ -0,0 +1,88 @@
+"""
+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, EmailStr
+from typing import Optional, Dict, TypedDict
+from uuid import UUID
+
+from app.models.schemas.user import UserResponse
+
+
+class BusinessHours(TypedDict):
+    start: str
+    end: str
+    enabled: bool
+
+
+class BusinessHoursDict(TypedDict):
+    monday: BusinessHours
+    tuesday: BusinessHours
+    wednesday: BusinessHours
+    thursday: BusinessHours
+    friday: BusinessHours
+    saturday: BusinessHours
+    sunday: BusinessHours
+
+
+class OrganizationBase(BaseModel):
+    name: str
+    domain: str
+    timezone: Optional[str] = 'UTC'
+    business_hours: Optional[BusinessHoursDict] = {
+        'monday': {'start': '09:00', 'end': '17:00', 'enabled': True},
+        'tuesday': {'start': '09:00', 'end': '17:00', 'enabled': True},
+        'wednesday': {'start': '09:00', 'end': '17:00', 'enabled': True},
+        'thursday': {'start': '09:00', 'end': '17:00', 'enabled': True},
+        'friday': {'start': '09:00', 'end': '17:00', 'enabled': True},
+        'saturday': {'start': '09:00', 'end': '17:00', 'enabled': False},
+        'sunday': {'start': '09:00', 'end': '17:00', 'enabled': False}
+    }
+    settings: Optional[Dict] = {}
+
+
+class OrganizationCreate(OrganizationBase):
+    admin_email: EmailStr
+    admin_name: str
+    admin_password: str
+
+
+class OrganizationUpdate(BaseModel):
+    name: Optional[str] = None
+    domain: Optional[str] = None
+    timezone: Optional[str] = None
+    business_hours: Optional[BusinessHoursDict] = None
+    settings: Optional[Dict] = None
+
+
+class OrganizationCreateResponse(OrganizationBase):
+    id: UUID
+    is_active: bool
+    access_token: Optional[str] = None
+    refresh_token: Optional[str] = None
+    token_type: Optional[str] = None
+    user: UserResponse
+
+    class Config:
+        from_attributes = True
+
+
+class OrganizationResponse(OrganizationBase):
+    id: UUID
+    is_active: bool
+    access_token: Optional[str] = None
+    refresh_token: Optional[str] = None
+    token_type: Optional[str] = None
+