fix: PushNotificationService 누락된 메서드 복원 및 DI 적용

- Controller: 생성자 DI로 PushNotificationService 주입
- Service: 12/18 커밋에서 삭제된 토큰 관리 메서드 복원
  - registerToken, unregisterToken, getUserTokens
  - getSettings, updateSettings
  - initializeDefaultSettings, getDefaultSound
- 기존 비즈니스 이벤트 푸시 기능(FcmSender) 유지

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

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

@@ -11,15 +11,17 @@
 
 class PushNotificationController extends Controller
 {
+    public function __construct(
+        private readonly PushNotificationService $service
+    ) {}
+
     /**
      * FCM 토큰 등록
      */
     public function registerToken(RegisterTokenRequest $request)
     {
         return ApiResponse::handle(function () use ($request) {
-            $service = new PushNotificationService;
-
-            return $service->registerToken($request->validated());
+            return $this->service->registerToken($request->validated());
         }, __('message.push.token_registered'));
     }
 
@@ -34,9 +36,7 @@ public function unregisterToken(Request $request)
                 throw new \InvalidArgumentException(__('error.push.token_required'));
             }
 
-            $service = new PushNotificationService;
-
-            return ['unregistered' => $service->unregisterToken($token)];
+            return ['unregistered' => $this->service->unregisterToken($token)];
         }, __('message.push.token_unregistered'));
     }
 
@@ -46,9 +46,7 @@ public function unregisterToken(Request $request)
     public function getTokens()
     {
         return ApiResponse::handle(function () {
-            $service = new PushNotificationService;
-
-            return $service->getUserTokens();
+            return $this->service->getUserTokens();
         });
     }
 
@@ -58,9 +56,7 @@ public function getTokens()
     public function getSettings()
     {
         return ApiResponse::handle(function () {
-            $service = new PushNotificationService;
-
-            return $service->getSettings();
+            return $this->service->getSettings();
         });
     }
 
@@ -70,9 +66,7 @@ public function getSettings()
     public function updateSettings(UpdateSettingsRequest $request)
     {
         return ApiResponse::handle(function () use ($request) {
-            $service = new PushNotificationService;
-
-            return $service->updateSettings($request->validated()['settings']);
+            return $this->service->updateSettings($request->validated()['settings']);
         }, __('message.push.settings_updated'));
     }