Time tracking, mentions, and richer tickets

A batch of upgrades to the day-to-day ticket experience:

• Time tracking on tickets.
• @mentions that notify the right teammate.
• Paste media straight into tickets and comments, screenshots included.
• Quick-open popups: click a ticket on the board or backlog to view it in a modal instead of a full page navigation.
• Search by ticket number to jump to any key instantly.