Add calendar event lifecycle management and "Add to Calendar" feature

- Migrate consulting_slots to consulting_sessions structure
- Add calendar_event_id to track Google Calendar events
- Create delete-calendar-event edge function for auto-cleanup
- Add "Tambah ke Kalender" button for members (OrderDetail, ConsultingHistory)
- Update create-google-meet-event to store calendar event ID
- Update handle-order-paid to use consulting_sessions table
- Remove deprecated create-meet-link function
- Add comprehensive documentation (CALENDAR_INTEGRATION.md, MIGRATION_GUIDE.md)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

supabase/migrations/20241228_add_calendar_event_id.sql

@@ -0,0 +1,12 @@
+-- Add calendar_event_id column to consulting_sessions
+-- This stores the Google Calendar event ID for later deletion
+
+ALTER TABLE consulting_sessions
+ADD COLUMN calendar_event_id TEXT;
+
+-- Create index for faster lookups
+CREATE INDEX idx_consulting_sessions_calendar_event
+ON consulting_sessions(calendar_event_id);
+
+-- Add comment
+COMMENT ON COLUMN consulting_sessions.calendar_event_id IS 'Google Calendar event ID - used to delete events when sessions are cancelled/refunded';