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>

languages/wp-prometheus.pot

@@ -2,7 +2,7 @@
 # This file is distributed under the GPL v2 or later.
 msgid ""
 msgstr ""
-"Project-Id-Version: WP Prometheus 0.2.0\n"
+"Project-Id-Version: WP Prometheus 0.3.0\n"
 "Report-Msgid-Bugs-To: https://src.bundespruefstelle.ch/magdev/wp-prometheus/issues\n"
 "POT-Creation-Date: 2026-02-02T00:00:00+00:00\n"
 "MIME-Version: 1.0\n"
@@ -28,6 +28,14 @@ msgstr ""
 msgid "Help"
 msgstr ""
 
+#: src/Admin/Settings.php
+msgid "Custom Metrics"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Dashboards"
+msgstr ""
+
 #: src/Admin/Settings.php
 msgid "License settings saved."
 msgstr ""
@@ -210,6 +218,18 @@ msgstr ""
 msgid "WooCommerce Customers (registered, guest)"
 msgstr ""
 
+#: src/Admin/Settings.php
+msgid "Reset Runtime Metrics"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Clear all accumulated runtime metric data."
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Reset Metrics"
+msgstr ""
+
 #: src/Admin/Settings.php
 msgid "Prometheus Configuration"
 msgstr ""
@@ -327,11 +347,249 @@ msgid "WooCommerce customers by type"
 msgstr ""
 
 #: src/Admin/Settings.php
-msgid "Custom Metrics"
+msgid "You can add custom metrics using the wp_prometheus_collect_metrics action:"
 msgstr ""
 
 #: src/Admin/Settings.php
-msgid "You can add custom metrics using the wp_prometheus_collect_metrics action:"
+msgid "Add Custom Metric"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Edit Custom Metric"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Metric Name"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Must follow Prometheus naming conventions."
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Help Text"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Description shown in Prometheus output."
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Value Type"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Static Value"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "WordPress Option"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Static Value:"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Option Name:"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "The name of the WordPress option to read."
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Labels"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Label name"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Add Label"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Label Values"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Value"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Add Value Row"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Enabled"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Save Metric"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Cancel"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Your Custom Metrics"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Name"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Status"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Actions"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Active"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Inactive"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Edit"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Delete"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "No custom metrics defined yet."
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Export / Import"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Export your custom metrics configuration for backup or transfer to another site."
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Export Metrics"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Import Metrics"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Import Options"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Skip existing metrics"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Overwrite existing metrics"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Rename duplicates"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Import"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Grafana Dashboard Templates"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Download pre-built Grafana dashboards for visualizing your WordPress metrics."
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Download"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Import instructions:"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Download the desired dashboard JSON file"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "In Grafana, go to Dashboards > Import"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Upload the JSON file or paste its contents"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Select your Prometheus data source"
+msgstr ""
+
+#: src/Admin/Settings.php
+msgid "Click Import"
+msgstr ""
+
+#: src/Metrics/CustomMetricBuilder.php
+msgid "Metric name is required."
+msgstr ""
+
+#: src/Metrics/CustomMetricBuilder.php
+msgid "Invalid metric name format."
+msgstr ""
+
+#: src/Metrics/CustomMetricBuilder.php
+msgid "A metric with this name already exists."
+msgstr ""
+
+#: src/Metrics/CustomMetricBuilder.php
+msgid "Help text is required."
+msgstr ""
+
+#: src/Metrics/CustomMetricBuilder.php
+msgid "Invalid value type."
+msgstr ""
+
+#: src/Metrics/CustomMetricBuilder.php
+msgid "Static value must be numeric."
+msgstr ""
+
+#: src/Metrics/CustomMetricBuilder.php
+msgid "Option name is required for option value type."
+msgstr ""
+
+#. translators: %d: Maximum number of labels
+#: src/Metrics/CustomMetricBuilder.php
+msgid "Maximum %d labels allowed."
+msgstr ""
+
+#: src/Metrics/CustomMetricBuilder.php
+msgid "Invalid label name format."
+msgstr ""
+
+#. translators: %d: Maximum number of label value combinations
+#: src/Metrics/CustomMetricBuilder.php
+msgid "Maximum %d label value combinations allowed."
+msgstr ""
+
+#: src/Metrics/CustomMetricBuilder.php
+msgid "Invalid JSON format."
+msgstr ""
+
+#: src/Metrics/CustomMetricBuilder.php
+msgid "Invalid export format."
 msgstr ""
 
 #: src/Plugin.php