Meeting booking: stand up Cal.com + firm setup flow

From Daniel's walkthrough: "No way to book a meeting."

The booking journey is fully built in the product (client: browse meeting types, pick a slot, confirm, reschedule/cancel, add-to-calendar; staff: create appointment types, admin connects the vendor). It looks missing because no scheduling vendor is connected: there is no Cal.com instance deployed and the firm has no appointment types, so the client page shows the "Your firm hasn't set up bookable meeting types yet" empty state.

To make it real: deploy self-hosted Cal.com (runbook docs/runbooks/calcom-selfhost.md, or Cal.com cloud per calcom-cloud.md), connect it in /staff/admin/settings, create 1-2 appointment types in /staff/scheduling. Then the client "book a slot" journey lights up end to end.