[Phone Connect] Add remote control support

I'm really enjoying DMS so far. I'd support for mouse movement and keyboard input from Kde connect as I tend to use these on a regular basis for my theatre setup. I'd also be willing to try and implement it.

The issue names the Phone Connect functionality and KDE Connect as the integration target, but provides no files, tests, or entry points. Locate the existing Phone Connect implementation first, then determine how mouse movement and keyboard input can be handled; done means both input types work through KDE Connect.

Written by the indexing model from the issue text.