[ContourClock] custom.html could remember previous font choices when updating?

### Affected hardware version

Bangle 2

### Your firmware version

2v24

### The bug

Due to the font selection via custom.html this app cannot be autoupdated from the apploader.
Also every time I update it manually I forget which fonts I have selected previously so I must go over the fonts and guess/pick them again. And it is hard to pick the one that I like because they look similar on the web and then slightly different on the watch so I select some and then finetune and select the final one directly on the watch. And next time when there is update I am lost which is the right one :-)

Is it possible that the custom.html would read settings from the installed app and preselected my previous fonts and possibly even allowed autoupdate when I do not want any change? I am not sure it can be done, maybe @gfwilliams knows?

### Installed apps

_No response_

Start with the ContourClock custom.html flow and inspect how the installed app stores and exposes its font settings. Then trace how the app loader handles customized apps and updates. Done means previously selected fonts are restored in custom.html and an update can proceed without changing them when no customization is requested.

Written by the indexing model from the issue text.