feat: Add custom metric builder, export/import, and Grafana dashboards (v0.3.0)

- Custom Metrics Builder with admin UI for gauge metrics
- Support for static values and WordPress option-based values
- JSON-based export/import with skip/overwrite/rename modes
- Three Grafana dashboard templates (overview, runtime, WooCommerce)
- New tabs: Custom Metrics and Dashboards
- Reset runtime metrics button

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

CLAUDE.md

@@ -18,6 +18,9 @@ This plugin provides a Prometheus `/metrics` endpoint and an extensible way to a
 - Cron job metrics (scheduled events, overdue, next run)
 - Transient cache metrics (total, expiring, expired)
 - WooCommerce integration (products, orders, revenue, customers)
+- Custom metric builder with admin UI (gauges with static or option-based values)
+- Metric export/import for backup and site migration
+- Grafana dashboard templates for easy visualization
 - Dedicated plugin settings under 'Settings/Metrics' menu
 - Extensible by other plugins using `wp_prometheus_collect_metrics` action hook
 - License management integration
@@ -30,11 +33,7 @@ This project is proudly **"vibe-coded"** using Claude.AI - the entire codebase w
 
 **Note for AI Assistants:** Clean this section after the specific features are done or new releases are made. Effective changes are tracked in `CHANGELOG.md`. Do not add completed versions here - document them in the Session History section at the end of this file.
 
-### Version 0.3.0 (Planned)
-
-- Custom metric builder in admin
-- Metric export/import
-- Grafana dashboard templates
+*No planned features at this time.*
 
 ## Technical Stack
 
@@ -214,6 +213,10 @@ wp-prometheus/
 │   └── release.yml          # CI/CD pipeline
 ├── assets/
 │   ├── css/                  # Admin/Frontend styles
+│   ├── dashboards/           # Grafana dashboard templates
+│   │   ├── wordpress-overview.json
+│   │   ├── wordpress-runtime.json
+│   │   └── wordpress-woocommerce.json
 │   └── js/
 │       └── admin.js          # Admin JavaScript
 ├── languages/                # Translation files
@@ -222,6 +225,7 @@ wp-prometheus/
 ├── releases/                 # Release packages
 ├── src/
 │   ├── Admin/
+│   │   ├── DashboardProvider.php # Grafana dashboard provider
 │   │   └── Settings.php      # Settings page
 │   ├── Endpoint/
 │   │   └── MetricsEndpoint.php  # /metrics endpoint
@@ -229,6 +233,7 @@ wp-prometheus/
 │   │   └── Manager.php       # License management
 │   ├── Metrics/
 │   │   ├── Collector.php        # Prometheus metrics collector
+│   │   ├── CustomMetricBuilder.php # Custom metric CRUD
 │   │   └── RuntimeCollector.php # Runtime metrics collector
 │   ├── Installer.php         # Activation/Deactivation
 │   ├── Plugin.php            # Main plugin class
@@ -285,6 +290,37 @@ add_action( 'wp_prometheus_collect_metrics', function( $collector ) {
 
 ## Session History
 
+### 2026-02-02 - Custom Metrics & Dashboards (v0.3.0)
+
+- Added Custom Metric Builder with full admin UI:
+  - `CustomMetricBuilder.php` - CRUD operations, validation, export/import
+  - Support for static values and WordPress option-based values
+  - Label support (max 5 labels, 50 value combinations)
+  - Prometheus naming convention validation (`[a-zA-Z_:][a-zA-Z0-9_:]*`)
+- Added Grafana Dashboard Templates:
+  - `DashboardProvider.php` - Dashboard file provider with path traversal protection
+  - `wordpress-overview.json` - General WordPress metrics
+  - `wordpress-runtime.json` - HTTP/DB performance metrics
+  - `wordpress-woocommerce.json` - WooCommerce store metrics
+- Added export/import functionality:
+  - JSON-based configuration export
+  - Three import modes: skip, overwrite, rename duplicates
+  - Version tracking in export format
+- Updated Settings page with new tabs:
+  - "Custom Metrics" tab with metric form and table
+  - "Dashboards" tab with download buttons
+  - "Reset Runtime Metrics" button in Metrics tab
+- Updated `Collector.php` to integrate custom metrics
+- Updated translation files with all new strings
+- **Key Learning**: Dynamic form handling in WordPress admin
+  - Use `wp_create_nonce()` with unique nonce names per AJAX action
+  - Localize script with `wp_localize_script()` for nonces and AJAX URL
+  - Always verify `current_user_can('manage_options')` in AJAX handlers
+- **Key Learning**: Grafana dashboard JSON format
+  - Use `${DS_PROMETHEUS}` for data source variable
+  - Schema version 39 for current Grafana compatibility
+  - Panels use `gridPos` for layout positioning
+
 ### 2026-02-02 - Extended Metrics (v0.2.0)
 
 - Added WooCommerce integration metrics (only when WooCommerce is active):