Roles, mentions, and a bug bash

Roles can now be mentioned in chat. Type @ followed by a role name and it'll resolve the same way a username does, notifying everyone who holds that role. @everyone works too — a reserved mention that pings every active member, not a role you assign to anyone.

Role assignment itself moved onto the member profile card, rather than living in a separate management screen. Click a member, and if you have permission to manage roles you'll see an inline checklist right there — toggle a role on or off without leaving the card.

This release also cleans up a batch of bugs that had been sitting around the Android client:

• Settings now actually shows your installed app version, instead of a blank dash.
• Your own profile picture renders correctly after syncing an identity via QR code.
• Mentions and reactions stop going stale after the app sits backgrounded for a while.
• The mention autocomplete dropdown is properly scrollable and wraps around with the arrow keys.

As always, this ships automatically to anyone already running the app — no reinstall needed unless you're setting up fresh. See the download page if you are.