feat(conversations): add notification mute functionality for conversations

- Rename Muted field to NotificationMuted across model, DTOs and converters
- Add UpdateNotificationMuted repository method with upsert support
- Add SetConversationNotificationMuted service method
- Add PUT /:id/notification_muted route for setting mute status
- Improve S3 storage resilience by skipping bucket check on access denied

internal/config/storage.go

@@ -35,10 +35,8 @@ func NewS3(cfg *S3Config) (*minio.Client, error) {
 
 	exists, err := client.BucketExists(ctx, cfg.Bucket)
 	if err != nil {
-		return nil, fmt.Errorf("failed to check bucket: %w", err)
-	}
-
-	if !exists {
+		// Access Denied 或网络不通时，跳过 bucket 检查，假定 bucket 已存在
+	} else if !exists {
 		if err := client.MakeBucket(ctx, cfg.Bucket, minio.MakeBucketOptions{
 			Region: cfg.Region,
 		}); err != nil {