feat: add Phase 2 features to map-editor plugin (rich marker content)

Implement marker editing modal with comprehensive content management:
- MarkerEditor.vue modal with custom overlay (replaces k-dialog)
- Edit marker on double-click or via edit button in list
- Required fields: title (validated), optional description
- Editable position (lat/lon) and custom icon support
- Content blocks system: add/remove/reorder text and image blocks
- French translations for all UI elements
- Click marker in list to center map on it with smooth animation
- Fix marker anchor to bottom (pin tip) for accurate positioning
- Auto-save with isDirty flag to detect any form changes

Modal features:
- Title field (required)
- Description textarea (optional)
- Position inputs (latitude/longitude)
- Icon selector (default or custom via UUID/filename)
- Content builder with text and image blocks
- Block reordering (up/down) and deletion
- Validation: save button enabled only when title filled and form modified

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

public/site/plugins/map-editor/src/components/map/MapPreview.vue

@@ -191,9 +191,11 @@ export default {
 
       try {
         // Create MapLibre marker
+        // Anchor at bottom-center (where the pin tip is)
         const marker = new maplibregl.Marker({
           element: el,
-          draggable: true
+          draggable: true,
+          anchor: 'bottom'
         })
           .setLngLat([markerData.position.lon, markerData.position.lat])
           .addTo(map.value);
@@ -223,6 +225,12 @@ export default {
           emit("marker-click", markerData.id);
         });
 
+        // Handle marker double-click
+        el.addEventListener("dblclick", (e) => {
+          e.stopPropagation();
+          emit("marker-dblclick", markerData.id);
+        });
+
         // Store marker reference
         markerElements.value.set(markerData.id, {
           marker,
@@ -259,10 +267,21 @@ export default {
       };
     }
 
+    function centerOnPosition(lat, lon) {
+      if (map.value && map.value.loaded()) {
+        map.value.flyTo({
+          center: [lon, lat],
+          zoom: map.value.getZoom(),
+          duration: 1000
+        });
+      }
+    }
+
     return {
       mapContainer,
       loading,
-      getCurrentCenter
+      getCurrentCenter,
+      centerOnPosition
     };
   }
 };