feat(models): add org_id to Article, PublishRecord, ContentMetrics, SearchRanking, GeoReadinessScore

- Add org_id column to 5 models with default='default'
- Update to_dict() methods for ContentMetrics, SearchRanking, GeoReadinessScore
- Add ALTER TABLE migrations in database.py init_db()
- Add org_id to 6 Pydantic response schemas
- Add require_role() helper factory in auth.py

platform/backend/app/api/auth.py

@@ -160,6 +160,16 @@ def get_current_admin(current_user: User = Depends(get_current_user)) -> User:
     if current_user.role != "admin":
         raise HTTPException(status_code=403, detail="需要管理员权限")
     return current_user
+
+def require_role(required_role: str):
+    """依赖项工厂：返回一个 FastAPI 依赖项，要求当前用户拥有指定角色。
+    管理员自动拥有所有角色权限。"""
+    def role_checker(current_user: User = Depends(get_current_user)):
+        if current_user.role != required_role and current_user.role != "admin":
+            raise HTTPException(status_code=403, detail=f"需要{required_role}角色权限")
+        return current_user
+    return role_checker
+
 @router.get("/me")
 def get_me(
     request: Request,