Shared team helpdesk inbox

Build a shared inbox for a small support team.

Core features:
1. Ingest email (via forwarding or IMAP) into tickets
2. Assign, tag, snooze, close
3. Canned replies, internal notes
4. Customer sees a portal with their ticket history
5. SLA timer per ticket, dashboard for response time

Data: tickets, messages, assignees, tags.
Must-haves: RLS by workspace, mentions, keyboard shortcuts.