feat: [fcm] Admin FCM API 추가 - MNG에서 API 호출로 FCM 발송

- AdminFcmController, AdminFcmService 추가
- FormRequest 검증 (AdminFcmSendRequest 등)
- Swagger 문서 추가 (AdminFcmApi.php)
- ApiKeyMiddleware: admin/fcm/* 화이트리스트 추가
- FCM 에러 메시지 i18n 추가

app/Http/Controllers/Api/V1/Admin/FcmController.php

@@ -0,0 +1,117 @@
+<?php
+
+namespace App\Http\Controllers\Api\V1\Admin;
+
+use App\Helpers\ApiResponse;
+use App\Http\Controllers\Controller;
+use App\Http\Requests\Admin\FcmHistoryRequest;
+use App\Http\Requests\Admin\FcmTokenListRequest;
+use App\Http\Requests\Admin\SendFcmRequest;
+use App\Services\AdminFcmService;
+use Illuminate\Http\JsonResponse;
+use Illuminate\Http\Request;
+
+class FcmController extends Controller
+{
+    public function __construct(
+        private readonly AdminFcmService $service
+    ) {}
+
+    /**
+     * FCM 발송
+     */
+    public function send(SendFcmRequest $request): JsonResponse
+    {
+        return ApiResponse::handle(function () use ($request) {
+            // sender_id는 MNG 관리자 ID로, 헤더에서 전달받음
+            $senderId = $request->header('X-Sender-Id');
+
+            $result = $this->service->send(
+                $request->validated(),
+                $senderId ? (int) $senderId : null
+            );
+
+            if (! $result['success']) {
+                return ApiResponse::error($result['message'], 422, $result);
+            }
+
+            return $result['data'];
+        }, __('message.fcm.sent'));
+    }
+
+    /**
+     * 대상 토큰 수 미리보기
+     */
+    public function previewCount(Request $request): JsonResponse
+    {
+        return ApiResponse::handle(function () use ($request) {
+            $count = $this->service->previewCount($request->only([
+                'tenant_id',
+                'user_id',
+                'platform',
+            ]));
+
+            return ['count' => $count];
+        });
+    }
+
+    /**
+     * 토큰 목록 조회
+     */
+    public function tokens(FcmTokenListRequest $request): JsonResponse
+    {
+        return ApiResponse::handle(function () use ($request) {
+            return $this->service->getTokens(
+                $request->validated(),
+                $request->integer('per_page', 20)
+            );
+        });
+    }
+
+    /**
+     * 토큰 통계
+     */
+    public function tokenStats(Request $request): JsonResponse
+    {
+        return ApiResponse::handle(function () use ($request) {
+            return $this->service->getTokenStats(
+                $request->integer('tenant_id')
+            );
+        });
+    }
+
+    /**
+     * 토큰 상태 토글
+     */
+    public function toggleToken(int $id): JsonResponse
+    {
+        return ApiResponse::handle(function () use ($id) {
+            return $this->service->toggleToken($id);
+        }, __('message.updated'));
+    }
+
+    /**
+     * 토큰 삭제
+     */
+    public function deleteToken(int $id): JsonResponse
+    {
+        return ApiResponse::handle(function () use ($id) {
+            $this->service->deleteToken($id);
+
+            return ['deleted' => true];
+        }, __('message.deleted'));
+    }
+
+    /**
+     * 발송 이력 조회
+     */
+    public function history(FcmHistoryRequest $request): JsonResponse
+    {
+        return ApiResponse::handle(function () use ($request) {
+            return $this->service->getHistory(
+                $request->validated(),
+                $request->integer('per_page', 20)
+            );
+        });
+    }
+}