feat: Phase 3.8 바로빌 세금계산서 연동 API 구현

- 마이그레이션: barobill_settings, tax_invoices 테이블 생성
- 모델: BarobillSetting (인증서 암호화), TaxInvoice (상태/유형 상수)
- 서비스: BarobillService (API 연동), TaxInvoiceService (CRUD, 발행/취소)
- 컨트롤러: BarobillSettingController, TaxInvoiceController
- FormRequest: 6개 요청 검증 클래스
- Swagger: API 문서 완성 (BarobillSettingApi, TaxInvoiceApi)

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

@@ -0,0 +1,54 @@
+<?php
+
+namespace App\Http\Controllers\Api\V1;
+
+use App\Helpers\ApiResponse;
+use App\Http\Controllers\Controller;
+use App\Http\Requests\BarobillSetting\SaveBarobillSettingRequest;
+use App\Services\BarobillService;
+
+class BarobillSettingController extends Controller
+{
+    public function __construct(
+        private BarobillService $barobillService
+    ) {}
+
+    /**
+     * 바로빌 설정 조회
+     */
+    public function show()
+    {
+        $setting = $this->barobillService->getSetting();
+
+        return ApiResponse::handle(
+            data: $setting,
+            message: __('message.fetched')
+        );
+    }
+
+    /**
+     * 바로빌 설정 저장
+     */
+    public function save(SaveBarobillSettingRequest $request)
+    {
+        $setting = $this->barobillService->saveSetting($request->validated());
+
+        return ApiResponse::handle(
+            data: $setting,
+            message: __('message.saved')
+        );
+    }
+
+    /**
+     * 연동 테스트
+     */
+    public function testConnection()
+    {
+        $result = $this->barobillService->testConnection();
+
+        return ApiResponse::handle(
+            data: $result,
+            message: __('message.barobill.connection_success')
+        );
+    }
+}