UI not compatible with mobile browsers

Several issues that would need to be fixed for the client to be usable on iOS/iPad (probably Androind, too). Maybe show a warning/error about incomplete mobile browsers support at least, if reliable detection is feasible?

Observations from trying on iPad Chrome briefly:

- *Doubletap doesn't open videos/folders* (apparently `dblclick` event doesn't fire on double taps with touch interfaces, would apparently need to be emulated manually by tap counting and timeouts)
- Video player play button doesn't start playback properly. Seek works fine though.
- Drawing submit causes an error of some kind, probably from video frame image capture not being supported. Drawing works fine, but submit to comment doesn't.

_Originally posted by @zen85 in https://github.com/elonen/clapshot/issues/63#issuecomment-2160054308_