[Feature] Show a warning message when attempting to view media that hasn't been transcoded yet

[ericswpark]

I have searched the existing feature requests to make sure this is not a duplicate request.

• Yes

The feature

Continuation of #14665. It would be great if Immich would warn the user if they attempt to play back a piece of media that hasn't been transcoded yet. Something like "This video is currently being converted into a format that your device supports, please check back later"?

Platform

• Server
• Web
• Mobile