Return a clear 503 response when Smart Search cannot reach any ML server

I have searched the existing feature requests, both open and closed, to make sure this is not a duplicate request. • Yes Platform • Server • Web • Mobile Problem When all configured machine-learning URLs are unavailable, a text Smart Search request returns a generic internal-server error: The server log contains the actual cause: This was reproduced on Immich v3.1.0 with a single remote ML URL configured through the admin UI and the remote worker intentionally offline. The local database and Immich containers were healthy. The current MachineLearningRepository.predict implementation tries all configured URLs and then throws a regular Error. ErrorInterceptor treats it as an unknown error and replaces it with the route-level generic 500 message. The web error handler already displays a server-provided message, so a more specific API response should also give the user an actionable toast. Relevant code: • • • Reproduction 1. Config…