Automated calendar sync and client notifications

Wired up Google Calendar sync so bookings are pulled automatically — 90 days back and 30 days ahead. It matches calendar attendees to client emails and upserts booking records. On top of that, clients now get email notifications when I add session notes, update a milestone, post a comment, add a deliverable, or assign them an action item. All fire-and-forget through Resend so nothing blocks the admin workflow. Notifications only go out to clients who have actually signed up for the portal.