feat: Add runtime metrics for HTTP requests and database queries (v0.1.0)

- Add RuntimeCollector class for tracking request lifecycle metrics
- Add wordpress_http_requests_total counter (method, status, endpoint)
- Add wordpress_http_request_duration_seconds histogram
- Add wordpress_db_queries_total counter (endpoint)
- Add wordpress_db_query_duration_seconds histogram (requires SAVEQUERIES)
- Update Collector to expose stored runtime metrics
- Add new settings options for enabling/disabling runtime metrics
- Create translation files (.pot, .po, .mo) for internationalization
- Update documentation and changelog

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

PLAN.md

@@ -91,6 +91,8 @@ wp-prometheus/
 
 The plugin provides the following default metrics (can be toggled in settings):
 
+### Static Metrics
+
 | Metric | Type | Labels | Description |
 |--------|------|--------|-------------|
 | wordpress_info | Gauge | version, php_version, multisite | WordPress installation info |
@@ -99,6 +101,15 @@ The plugin provides the following default metrics (can be toggled in settings):
 | wordpress_comments_total | Gauge | status | Total comments by status |
 | wordpress_plugins_total | Gauge | status | Total plugins (active/inactive) |
 
+### Runtime Metrics
+
+| Metric                                   | Type      | Labels                   | Description                           |
+| ---------------------------------------- | --------- | ------------------------ | ------------------------------------- |
+| wordpress_http_requests_total            | Counter   | method, status, endpoint | Total HTTP requests                   |
+| wordpress_http_request_duration_seconds  | Histogram | method, endpoint         | Request duration distribution         |
+| wordpress_db_queries_total               | Counter   | endpoint                 | Total database queries                |
+| wordpress_db_query_duration_seconds      | Histogram | endpoint                 | Query duration (requires SAVEQUERIES) |
+
 ## Extensibility
 
 ### Adding Custom Metrics
@@ -150,12 +161,6 @@ https://example.com/metrics/?token=your-auth-token
 
 ## Future Enhancements
 
-### Version 0.1.0
-
-- Request/Response timing metrics
-- HTTP status code counters
-- Database query metrics
-
 ### Version 0.2.0
 
 - WooCommerce integration metrics