Replace Gorush with direct APNs/FCM integration

- Add direct APNs client using sideshow/apns2 for iOS push
- Add direct FCM client using legacy HTTP API for Android push
- Remove Gorush dependency (no external push server needed)
- Update all services/handlers to use new push.Client
- Update config for APNS_PRODUCTION flag

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

internal/services/notification_service.go

@@ -22,14 +22,14 @@ var (
 // NotificationService handles notification business logic
 type NotificationService struct {
 	notificationRepo *repositories.NotificationRepository
-	gorushClient     *push.GorushClient
+	pushClient       *push.Client
 }
 
 // NewNotificationService creates a new notification service
-func NewNotificationService(notificationRepo *repositories.NotificationRepository, gorushClient *push.GorushClient) *NotificationService {
+func NewNotificationService(notificationRepo *repositories.NotificationRepository, pushClient *push.Client) *NotificationService {
 	return &NotificationService{
 		notificationRepo: notificationRepo,
-		gorushClient:     gorushClient,
+		pushClient:       pushClient,
 	}
 }
 
@@ -123,8 +123,8 @@ func (s *NotificationService) CreateAndSendNotification(ctx context.Context, use
 	pushData["notification_id"] = string(rune(notification.ID))
 
 	// Send push notification
-	if s.gorushClient != nil {
-		err = s.gorushClient.SendToAll(ctx, iosTokens, androidTokens, title, body, pushData)
+	if s.pushClient != nil {
+		err = s.pushClient.SendToAll(ctx, iosTokens, androidTokens, title, body, pushData)
 		if err != nil {
 			s.notificationRepo.SetError(notification.ID, err.Error())
 			return err