docs: Add database query timing documentation and dashboard panel (v0.4.7)

- Add Query Duration Distribution panel to Grafana Runtime dashboard
- Add wordpress_db_query_duration_seconds to Help tab metrics reference
- Add SAVEQUERIES documentation section to README
- Update translation files with new strings

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

assets/dashboards/wordpress-runtime.json

@@ -946,6 +946,95 @@
       ],
       "title": "Average Query Duration (Overall)",
       "type": "stat"
+    },
+    {
+      "datasource": {
+        "type": "prometheus",
+        "uid": "${DS_PROMETHEUS}"
+      },
+      "fieldConfig": {
+        "defaults": {
+          "color": {
+            "mode": "palette-classic"
+          },
+          "custom": {
+            "axisBorderShow": false,
+            "axisCenteredZero": false,
+            "axisColorMode": "text",
+            "axisLabel": "",
+            "axisPlacement": "auto",
+            "fillOpacity": 80,
+            "gradientMode": "none",
+            "hideFrom": {
+              "legend": false,
+              "tooltip": false,
+              "viz": false
+            },
+            "lineWidth": 1,
+            "scaleDistribution": {
+              "type": "linear"
+            },
+            "thresholdsStyle": {
+              "mode": "off"
+            }
+          },
+          "mappings": [],
+          "thresholds": {
+            "mode": "absolute",
+            "steps": [
+              {
+                "color": "green",
+                "value": null
+              }
+            ]
+          }
+        },
+        "overrides": []
+      },
+      "gridPos": {
+        "h": 8,
+        "w": 24,
+        "x": 0,
+        "y": 39
+      },
+      "id": 15,
+      "options": {
+        "barRadius": 0,
+        "barWidth": 0.97,
+        "fullHighlight": false,
+        "groupWidth": 0.7,
+        "legend": {
+          "calcs": [],
+          "displayMode": "list",
+          "placement": "bottom",
+          "showLegend": true
+        },
+        "orientation": "horizontal",
+        "showValue": "auto",
+        "stacking": "none",
+        "tooltip": {
+          "mode": "single",
+          "sort": "none"
+        },
+        "xTickLabelRotation": 0,
+        "xTickLabelSpacing": 0
+      },
+      "targets": [
+        {
+          "datasource": {
+            "type": "prometheus",
+            "uid": "${DS_PROMETHEUS}"
+          },
+          "editorMode": "code",
+          "expr": "sum(wordpress_db_query_duration_seconds_bucket) by (le)",
+          "format": "table",
+          "instant": true,
+          "legendFormat": "{{le}}",
+          "refId": "A"
+        }
+      ],
+      "title": "Query Duration Distribution (Buckets)",
+      "type": "barchart"
     }
   ],
   "refresh": "30s",