feat: simple failed request handling (#474)

When a movie or series is added with radarr or sonarr, if it fails, this changes the media state to
unknown and sends a notification to admins. Client side this will look like a failed state along
with a retry button that will delete the request and re-queue it.

server/lib/notifications/index.ts

@@ -5,7 +5,8 @@ export enum Notification {
   MEDIA_PENDING = 2,
   MEDIA_APPROVED = 4,
   MEDIA_AVAILABLE = 8,
-  TEST_NOTIFICATION = 16,
+  MEDIA_FAILED = 16,
+  TEST_NOTIFICATION = 32,
 }
 
 class NotificationManager {