W-04: Add showProjectInviteToast with Accept/Decline buttons in
NotificationToaster, matching the connection/calendar/event invite
toast pattern. Wired into both initial-load and new-notification flows.
W-06: Delete rejected ProjectMember rows on rejection instead of
accumulating them with status='rejected'. Prevents indefinite growth.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>