Show local usage data

It could be interesting to show local, user-specific usage data, kind of like Steam's "time played" on the app listing. This could be combined with the total amount paid to communicate value.

This of course assumes we can get the usage data (e.g. from Zeitgeist?), and locally store the amount paid.

Thanks to @ted-gould via [Mastodon](https://social.gould.cx/@ted/99474736508309757) for the idea. :wink:

Start with the app listing flow and investigate whether usage data can be obtained from Zeitgeist and whether the locally stored amount paid is already supported. No files or tests are named, and the issue does not define the data model or presentation. Done would require agreed requirements for showing usage and total paid.

Written by the indexing model from the issue text.