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/ItemsController.php

@@ -103,6 +103,23 @@ public function update(int $id, ItemUpdateRequest $request)
         }, __('message.item.updated'));
     }
 
+    /**
+     * 품목 통계 조회
+     *
+     * GET /api/v1/items/stats
+     */
+    public function stats(Request $request)
+    {
+        return ApiResponse::handle(function () use ($request) {
+            $params = [
+                'item_type' => $request->input('type') ?? $request->input('item_type'),
+                'group_id' => $request->input('group_id'),
+            ];
+
+            return $this->service->stats($params);
+        }, __('message.fetched'));
+    }
+
     /**
      * 품목 삭제 (동적 테이블 라우팅, Soft Delete)
      *