feat: 공통 모듈 추가 (엑셀 내보내기, 계정과목 일괄변경)

Phase 0 - 공통 모듈:
- ExportService.php 생성 (Maatwebsite/Excel 기반 엑셀 내보내기)
- BulkUpdateAccountCodeRequest.php 생성 (계정과목 일괄변경 유효성 검사)

Phase 1 - 계정과목 일괄변경:
- WithdrawalController/Service: bulkUpdateAccountCode 메서드 추가
- DepositController/Service: bulkUpdateAccountCode 메서드 추가
- POST /v1/withdrawals/bulk-update-account-code
- POST /v1/deposits/bulk-update-account-code

Phase 2 - 엑셀 내보내기:
- AttendanceController/Service: export, getExportData 메서드 추가
- SalaryController/Service: export, getExportData 메서드 추가
- GET /v1/attendances/export
- GET /v1/salaries/export

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

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

@@ -7,13 +7,16 @@
 use App\Http\Requests\V1\Salary\BulkUpdateStatusRequest;
 use App\Http\Requests\V1\Salary\StoreSalaryRequest;
 use App\Http\Requests\V1\Salary\UpdateSalaryRequest;
+use App\Services\ExportService;
 use App\Services\SalaryService;
 use Illuminate\Http\Request;
+use Symfony\Component\HttpFoundation\BinaryFileResponse;
 
 class SalaryController extends Controller
 {
     public function __construct(
-        private readonly SalaryService $service
+        private readonly SalaryService $service,
+        private readonly ExportService $exportService
     ) {}
 
     /**
@@ -123,4 +126,33 @@ public function statistics(Request $request)
 
         return ApiResponse::success($stats, __('message.fetched'));
     }
+
+    /**
+     * 급여 엑셀 내보내기
+     * GET /v1/salaries/export
+     */
+    public function export(Request $request): BinaryFileResponse
+    {
+        $params = $request->only([
+            'search',
+            'year',
+            'month',
+            'status',
+            'employee_id',
+            'start_date',
+            'end_date',
+            'sort_by',
+            'sort_dir',
+        ]);
+
+        $exportData = $this->service->getExportData($params);
+        $filename = '급여현황_'.date('Ymd_His');
+
+        return $this->exportService->download(
+            $exportData['data'],
+            $exportData['headings'],
+            $filename,
+            '급여현황'
+        );
+    }
 }