Add Grafana dashboard and wp-prometheus integration (v0.7.5)

- Add example Grafana dashboard with 24 panels for license metrics
- Register dashboard with wp-prometheus via hook
- Add dashboard documentation with PromQL examples and alerting rules
- Update README with monitoring section

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

README.md

@@ -393,6 +393,38 @@ The plugin sends automatic email notifications (configurable via WooCommerce > S
 - **Expiration Warning (1 day)**: Urgent reminder sent 1 day before expiration
 - **License Expired**: Notification when a license auto-expires
 
+## Monitoring with Prometheus & Grafana
+
+The plugin integrates with [wp-prometheus](https://src.bundespruefstelle.ch/magdev/wp-prometheus) to expose metrics for monitoring and alerting.
+
+### Enable Metrics
+
+1. Install and configure the wp-prometheus plugin
+2. Go to WooCommerce > Settings > Licensed Products > Metrics
+3. Enable "Prometheus Metrics"
+
+### Available Metrics
+
+**Gauges:**
+
+- `wclp_licenses_total{status}` - License counts by status
+- `wclp_licenses_lifetime_total` - Lifetime licenses
+- `wclp_licenses_expiring_soon` - Licenses expiring within 30 days
+- `wclp_downloads_total` - Total file downloads
+- `wclp_versions_active_total` - Active product versions
+
+**Counters:**
+
+- `wclp_api_requests_total{endpoint,result}` - API requests by endpoint and result
+- `wclp_rate_limit_exceeded_total{endpoint}` - Rate limit events
+- `wclp_validation_errors_total{error_type}` - Validation errors by type
+
+### Grafana Dashboard
+
+An example Grafana dashboard is included at [docs/grafana-dashboard.json](docs/grafana-dashboard.json).
+
+See [docs/grafana-dashboard.md](docs/grafana-dashboard.md) for installation instructions, panel descriptions, and alerting examples.
+
 ## Changelog
 
 See [CHANGELOG.md](CHANGELOG.md) for version history and changes.