fix: Sort sources alphabetically in UI for consistent display

Changed Sources list and dropdown to sort alphabetically by name instead of
dynamically by last data arrival time. This provides a stable, predictable
order that is less distracting during use.

- Modified updateSourcesLegend() in map-manager.js to sort sources by name
- Modified updateSourceFilter() in ui-manager.js to maintain consistent sorting
- Sources now use localeCompare() for proper alphabetical ordering

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

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

assets/static/js/modules/map-manager.js

@@ -199,7 +199,12 @@ export class MapManager {
         
         legend.innerHTML = '';
         
-        for (const [id, source] of this.sourcesData) {
+        // Sort sources alphabetically by name
+        const sortedSources = Array.from(this.sourcesData.values()).sort((a, b) => 
+            a.name.localeCompare(b.name)
+        );
+        
+        for (const source of sortedSources) {
             const item = document.createElement('div');
             item.className = 'legend-item';
             item.innerHTML = `