feat: Improve aircraft legend clarity and icon differentiation

Resolves issue #13 by implementing comprehensive aircraft legend improvements:

## New Features
- **Size-based aircraft icons**: Created distinct SVG icons for light, medium, large, and heavy aircraft with progressively larger visual representations
- **Visual aircraft icons in legend**: Replaced colored squares with actual aircraft silhouettes showing relative sizes and types
- **Enhanced categorization**: Added military category to legend and improved icon selection logic

## Improvements
- **Better differentiation**: Each weight class now has a unique icon shape, not just color
- **Accurate ADS-B mapping**: Icons correctly map to decoded ADS-B emitter categories
- **Clearer legend display**: Users can now see actual aircraft shapes instead of generic colored rectangles

## Technical Changes
- Created 4 new SVG icons: light.svg, medium.svg, large.svg, heavy.svg
- Updated legend HTML to embed aircraft SVG icons inline
- Enhanced JavaScript logic to better match categories to appropriate icon types
- Simplified color mapping function for cleaner code

This addresses the original concerns about confusing legend entries and lack of visual differentiation between aircraft types.

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

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

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

@@ -331,60 +331,48 @@ export class AircraftManager {
     }
     
     getAircraftIconType(aircraft) {
-        // For icon selection, we still need basic categories
-        // This determines which SVG shape to use
+        // For icon selection, determine which SVG shape to use based on category
         if (aircraft.OnGround) return 'ground';
         
         if (aircraft.Category) {
             const cat = aircraft.Category.toLowerCase();
             
-            // Map to basic icon types for visual representation
+            // Specialized aircraft types
             if (cat.includes('helicopter') || cat.includes('rotorcraft')) return 'helicopter';
             if (cat.includes('military') || cat.includes('fighter') || cat.includes('bomber')) return 'military';
-            if (cat.includes('cargo') || cat.includes('heavy') || cat.includes('super')) return 'cargo';
-            if (cat.includes('light') || cat.includes('glider') || cat.includes('ultralight')) return 'ga';
+            if (cat.includes('glider') || cat.includes('ultralight')) return 'ga';
+            
+            // Weight-based categories with specific icons
+            if (cat.includes('light') && cat.includes('7000')) return 'light';
+            if (cat.includes('medium') && cat.includes('7000-34000')) return 'medium';
+            if (cat.includes('large') && cat.includes('34000-136000')) return 'large';
+            if (cat.includes('heavy') && cat.includes('136000')) return 'heavy';
+            if (cat.includes('high vortex')) return 'large'; // Use large icon for high vortex
+            
+            // Fallback category matching
+            if (cat.includes('heavy') || cat.includes('super')) return 'heavy';
+            if (cat.includes('large')) return 'large';
+            if (cat.includes('medium')) return 'medium'; 
+            if (cat.includes('light')) return 'light';
         }
         
-        // Default commercial icon for everything else
-        return 'commercial';
+        // Default to medium icon for unknown aircraft
+        return 'medium';
     }
 
     getAircraftColor(type, aircraft) {
-        // Special colors for specific types
-        if (type === 'military') return '#ff4444';
-        if (type === 'helicopter') return '#ff00ff';
-        if (type === 'ground') return '#888888';
-        if (type === 'ga') return '#ffff00';
-        
-        // For commercial and cargo types, use weight-based colors
-        if (aircraft && aircraft.Category) {
-            const cat = aircraft.Category.toLowerCase();
-            
-            // Check for specific weight ranges in the category string
-            // Light aircraft (< 7000kg) - Sky blue
-            if (cat.includes('light')) {
-                return '#00bfff';
-            }
-            // Medium aircraft (7000-34000kg) - Green  
-            if (cat.includes('medium')) {
-                return '#00ff88';
-            }
-            // High Vortex Large - Red-orange (special wake turbulence category)
-            if (cat.includes('high vortex')) {
-                return '#ff4500';
-            }
-            // Large aircraft (34000-136000kg) - Orange
-            if (cat.includes('large')) {
-                return '#ff8c00';
-            }
-            // Heavy aircraft (> 136000kg) - Red
-            if (cat.includes('heavy') || cat.includes('super')) {
-                return '#ff0000';
-            }
+        // Color mapping based on aircraft type/size
+        switch (type) {
+            case 'military': return '#ff4444';  // Red-orange for military
+            case 'helicopter': return '#ff00ff'; // Magenta for helicopters
+            case 'ground': return '#888888';    // Gray for ground vehicles
+            case 'ga': return '#ffff00';        // Yellow for general aviation
+            case 'light': return '#00bfff';     // Sky blue for light aircraft
+            case 'medium': return '#00ff88';    // Green for medium aircraft
+            case 'large': return '#ff8c00';     // Orange for large aircraft
+            case 'heavy': return '#ff0000';     // Red for heavy aircraft
+            default: return '#00ff88';          // Default green for unknown
         }
-        
-        // Default to green for unknown commercial aircraft
-        return '#00ff88';
     }