feat:E-Sign 전자계약 서명 솔루션 백엔드 구현

- 마이그레이션 4개 (esign_contracts, esign_signers, esign_sign_fields, esign_audit_logs)
- 모델 4개 (EsignContract, EsignSigner, EsignSignField, EsignAuditLog)
- 서비스 4개 (EsignContractService, EsignSignService, EsignPdfService, EsignAuditService)
- 컨트롤러 2개 (EsignContractController, EsignSignController)
- FormRequest 4개 (ContractStore, FieldConfigure, SignSubmit, SignReject)
- Mail 1개 (EsignRequestMail + 이메일 템플릿)
- API 라우트 (인증 계약 관리 + 토큰 기반 서명 프로세스)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/Http/Controllers/Api/V1/ESign/EsignContractController.php

@@ -0,0 +1,116 @@
+<?php
+
+namespace App\Http\Controllers\Api\V1\ESign;
+
+use App\Helpers\ApiResponse;
+use App\Http\Controllers\Controller;
+use App\Http\Requests\ESign\ContractStoreRequest;
+use App\Http\Requests\ESign\FieldConfigureRequest;
+use App\Services\ESign\EsignContractService;
+use App\Services\ESign\EsignPdfService;
+use Illuminate\Http\JsonResponse;
+use Illuminate\Http\Request;
+use Illuminate\Support\Facades\Storage;
+
+class EsignContractController extends Controller
+{
+    public function __construct(
+        private EsignContractService $service,
+        private EsignPdfService $pdfService,
+    ) {}
+
+    public function index(Request $request): JsonResponse
+    {
+        return ApiResponse::handle(function () use ($request) {
+            return $this->service->list($request->all());
+        }, __('message.fetched'));
+    }
+
+    public function show(int $id): JsonResponse
+    {
+        return ApiResponse::handle(function () use ($id) {
+            return $this->service->show($id);
+        }, __('message.fetched'));
+    }
+
+    public function store(ContractStoreRequest $request): JsonResponse
+    {
+        return ApiResponse::handle(function () use ($request) {
+            return $this->service->create($request->validated() + ['file' => $request->file('file')]);
+        }, __('message.created'));
+    }
+
+    public function cancel(int $id): JsonResponse
+    {
+        return ApiResponse::handle(function () use ($id) {
+            return $this->service->cancel($id);
+        }, __('message.esign.cancelled'));
+    }
+
+    public function configureFields(int $id, FieldConfigureRequest $request): JsonResponse
+    {
+        return ApiResponse::handle(function () use ($id, $request) {
+            return $this->service->configureFields($id, $request->validated()['fields']);
+        }, __('message.esign.fields_configured'));
+    }
+
+    public function send(int $id): JsonResponse
+    {
+        return ApiResponse::handle(function () use ($id) {
+            return $this->service->send($id);
+        }, __('message.esign.sent'));
+    }
+
+    public function remind(int $id): JsonResponse
+    {
+        return ApiResponse::handle(function () use ($id) {
+            return $this->service->remind($id);
+        }, __('message.esign.reminded'));
+    }
+
+    public function stats(): JsonResponse
+    {
+        return ApiResponse::handle(function () {
+            return $this->service->stats();
+        }, __('message.fetched'));
+    }
+
+    public function download(int $id): \Symfony\Component\HttpFoundation\StreamedResponse|JsonResponse
+    {
+        try {
+            $contract = $this->service->show($id);
+            $filePath = $contract->signed_file_path ?? $contract->original_file_path;
+
+            if (! $filePath || ! Storage::disk('local')->exists($filePath)) {
+                return ApiResponse::error(__('error.esign.file_not_found'), 404);
+            }
+
+            $fileName = $contract->original_file_name ?? 'contract.pdf';
+
+            return Storage::disk('local')->download($filePath, $fileName);
+        } catch (\Throwable $e) {
+            return ApiResponse::error($e->getMessage(), 500);
+        }
+    }
+
+    public function verify(int $id): JsonResponse
+    {
+        return ApiResponse::handle(function () use ($id) {
+            $contract = $this->service->show($id);
+
+            if (! $contract->original_file_path || ! $contract->original_file_hash) {
+                return ['verified' => false, 'message' => '파일 정보가 없습니다.'];
+            }
+
+            $isValid = $this->pdfService->verifyIntegrity(
+                $contract->original_file_path,
+                $contract->original_file_hash
+            );
+
+            return [
+                'verified' => $isValid,
+                'original_hash' => $contract->original_file_hash,
+            ];
+        }, __('message.esign.verified'));
+    }
+}