feat: WordPress Monitor API + Site Availability Checker

- Add POST /api/wp-monitor endpoint for WP plugin data
- Add GET /api/wp-monitor for listing monitored sites
- Add checkSiteAvailability() function for HTTP health checks
- Add checkAllSitesAvailability() for batch checking
- Add /api/scripts/check-sites.ts for cron execution
- Add POST /api/monitor/check-sites for manual trigger

DeskCRM Task: #1556

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

.env.example

@@ -8,5 +8,8 @@ DB_NAME=ealmeida_desk24
 API_PORT=3001
 FRONTEND_URL=http://localhost:5173
 
+# Hetzner Cloud API
+HETZNER_TOKEN=your_hetzner_api_token_here
+
 # Production URLs
 # FRONTEND_URL=https://dash.descomplicar.pt