fix(API): Controller 타입 및 코드 정리

- FcmController, EstimateController, ItemsController 개선
- LoanController, PositionController 수정
- ReceivablesController, SalaryController 수정
- StructureReviewController 수정

Co-Authored-By: Claude <noreply@anthropic.com>

app/Http/Controllers/Api/V1/PositionController.php

@@ -71,4 +71,4 @@ public function reorder(PositionReorderRequest $request)
             return $this->service->reorder($request->validated()['items']);
         }, __('message.reordered'));
     }
-}
+}