refactor(system): extract admin details conversion to helper function

- Add `_system_admin_details()` helper function to convert database Admin model to AdminDetails
- Import Admin model and AdminRoleData from respective modules
- Replace inline AdminDetails.model_validate() call with helper function in get_system_stats()
- Improves code reusability and maintainability for admin details conversion logic

Author: x0sina

app/operation/system.py

@@ -7,15 +7,26 @@
 from app.db.crud.admin import get_admin
 from app.db.crud.general import get_system_usage
 from app.db.crud.user import count_online_users, get_users_count_by_status
-from app.db.models import UserStatus
-from app.models.admin import AdminDetails
+from app.db.models import Admin, UserStatus
+from app.models.admin import AdminDetails, AdminRoleData
 from app.models.system import InboundSummary, SystemStats
 from app.operation.permissions import PermissionDenied, enforce_permission, is_scope_all
 from app.utils.system import cpu_usage, disk_usage, get_uptime, memory_usage
 
 from . import BaseOperation
 
 
+def _system_admin_details(db_admin: Admin) -> AdminDetails:
+    return AdminDetails(
+        id=db_admin.id,
+        username=db_admin.username,
+        used_traffic=int(db_admin.used_traffic or 0),
+        data_limit=db_admin.data_limit,
+        status=db_admin.status,
+        role=AdminRoleData.model_validate(db_admin.role) if db_admin.role is not None else None,
+    )
+
+
 class SystemOperation(BaseOperation):
     @staticmethod
     async def get_system_stats(db: AsyncSession, admin: AdminDetails, admin_username: str | None = None) -> SystemStats:
@@ -43,7 +54,7 @@ async def get_system_stats(db: AsyncSession, admin: AdminDetails, admin_username
             if admin.is_owner or can_read_admins:
                 db_admin = await get_admin(db, admin_username, load_users=False, load_usage_logs=False)
                 if db_admin is not None:
-                    admin_param = AdminDetails.model_validate(db_admin)
+                    admin_param = _system_admin_details(db_admin)
             else:
                 admin_param = admin
         elif not admin.is_owner: