Fix source popup closing immediately after opening

Problem: Source markers were being recreated on every WebSocket update
(every second), which destroyed any open popups.

Solution: Modified updateSourceMarkers() to:
- Only remove markers for sources that no longer exist
- Update existing markers in-place instead of recreating them
- Preserve open popups by updating content instead of recreating markers
- Only create new markers when sources are actually added

This ensures that clicking on a source marker opens a popup that stays
open for user interaction, similar to aircraft popups.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

static/js/app.js

@@ -333,27 +333,50 @@ class SkyView {
     }
 
     updateSourceMarkers() {
-        // Clear existing source markers
-        this.sourceMarkers.forEach(marker => this.map.removeLayer(marker));
-        this.sourceMarkers.clear();
+        // Remove markers for sources that no longer exist
+        const currentSourceIds = new Set(this.sourcesData.keys());
+        for (const [id, marker] of this.sourceMarkers) {
+            if (!currentSourceIds.has(id)) {
+                this.map.removeLayer(marker);
+                this.sourceMarkers.delete(id);
+            }
+        }
         
-        // Add source markers
+        // Update or create markers for current sources
         for (const [id, source] of this.sourcesData) {
             if (source.latitude && source.longitude) {
-                const marker = L.circleMarker([source.latitude, source.longitude], {
-                    radius: source.active ? 10 : 6,
-                    fillColor: source.active ? '#00d4ff' : '#666666',
-                    color: '#ffffff',
-                    weight: 2,
-                    fillOpacity: 0.8,
-                    className: 'source-marker'
-                }).addTo(this.map);
-                
-                marker.bindPopup(this.createSourcePopupContent(source), {
-                    maxWidth: 300
-                });
-                
-                this.sourceMarkers.set(id, marker);
+                if (this.sourceMarkers.has(id)) {
+                    // Update existing marker
+                    const marker = this.sourceMarkers.get(id);
+                    
+                    // Update marker style if status changed
+                    marker.setStyle({
+                        radius: source.active ? 10 : 6,
+                        fillColor: source.active ? '#00d4ff' : '#666666',
+                        fillOpacity: 0.8
+                    });
+                    
+                    // Update popup content if it's open
+                    if (marker.isPopupOpen()) {
+                        marker.setPopupContent(this.createSourcePopupContent(source));
+                    }
+                } else {
+                    // Create new marker
+                    const marker = L.circleMarker([source.latitude, source.longitude], {
+                        radius: source.active ? 10 : 6,
+                        fillColor: source.active ? '#00d4ff' : '#666666',
+                        color: '#ffffff',
+                        weight: 2,
+                        fillOpacity: 0.8,
+                        className: 'source-marker'
+                    }).addTo(this.map);
+                    
+                    marker.bindPopup(this.createSourcePopupContent(source), {
+                        maxWidth: 300
+                    });
+                    
+                    this.sourceMarkers.set(id, marker);
+                }
             }
         }