Improve aircraft marker visibility

- Increase aircraft marker size from 20px to 24px
- Add aircraft wing elements for better aircraft appearance
- Use bright green color for aircraft with position data
- Add stronger drop shadow for better contrast against map
- Gray out aircraft without position data

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

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

static/css/style.css

@@ -229,10 +229,9 @@ body {
 }
 
 .aircraft-marker {
-    width: 20px;
-    height: 20px;
     transform: rotate(0deg);
-    filter: drop-shadow(0 0 2px rgba(0,0,0,0.8));
+    filter: drop-shadow(0 0 4px rgba(0,0,0,0.9));
+    z-index: 1000;
 }
 
 .aircraft-popup {