feat: add shared notification, communication, and export services for bookings, courses, and events; introduce btree_gist extension and new booking atomic function

apps/web/supabase/migrations/20260417000003600_booking_function_grants.sql

@@ -0,0 +1 @@
+GRANT EXECUTE ON FUNCTION public.create_booking_atomic(uuid, uuid, uuid, date, date, integer, integer, text, numeric, text) TO authenticated;