Implement Phase 9: Prometheus Metrics (v0.9.0)

- Add Prometheus metrics integration via wp-prometheus hooks
- Create Grafana dashboard JSON with 24 panels
- Add metrics settings tab with enable/disable toggle
- Expose inventory, booking, occupancy, revenue, and guest metrics

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

CHANGELOG.md

@@ -5,6 +5,36 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.9.0] - 2026-02-03
+
+### Added
+
+- Prometheus Metrics Integration:
+  - New `src/Integration/Prometheus.php` class for metrics collection
+  - Integration with wp-prometheus plugin via `wp_prometheus_collect_metrics` hook
+  - Inventory metrics: buildings total, rooms by status, services by status
+  - Booking metrics: bookings by status, check-ins/check-outs today, upcoming 7 days, avg duration
+  - Guest metrics: total guests, guests by status, repeat guests, new guests this month
+  - Occupancy metrics: current rate, monthly rate, occupied rooms, total bed capacity
+  - Revenue metrics: this month, YTD, average booking value, services revenue
+- Grafana Dashboard:
+  - Pre-configured dashboard at `assets/grafana/wp-bnb-dashboard.json`
+  - Automatic registration with wp-prometheus dashboard provider
+  - Occupancy gauges with color-coded thresholds
+  - Pie charts for bookings, rooms, and guests by status
+  - Revenue and guest statistics panels
+  - Responsive grid layout with 24 panels
+- Settings page Metrics tab:
+  - Enable/disable metrics collection toggle
+  - WP Prometheus detection with status indicator
+  - Complete metrics reference table
+  - Dashboard file location and export info
+
+### Changed
+
+- Plugin.php updated to initialize Prometheus integration
+- Settings page now has six tabs: General, Pricing, License, Updates, Metrics
+
 ## [0.8.0] - 2026-02-03
 
 ### Added