feat: Add WooCommerce, cron, and transient metrics (v0.2.0)

- WooCommerce integration metrics (products, orders, revenue, customers)
- Cron job metrics (events by hook, overdue count, next run timestamp)
- Transient cache metrics (total, expiring, expired)
- Support for WooCommerce HPOS storage
- Updated settings page with new metric categories
- Updated translations and documentation

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

PLAN.md

@@ -161,12 +161,6 @@ https://example.com/metrics/?token=your-auth-token
 
 ## Future Enhancements
 
-### Version 0.2.0
-
-- WooCommerce integration metrics
-- Cron job metrics
-- Transient cache metrics
-
 ### Version 0.3.0
 
 - Custom metric builder in admin