Improve aircraft icons and add weight-based color coding

- Replaced simple geometric shapes with detailed, realistic SVG icons for all aircraft types
- Implemented color differentiation based on aircraft weight categories:
  * Light (<7000kg): Sky blue
  * Medium (7000-34000kg): Green
  * Large (34000-136000kg): Orange
  * Heavy (>136000kg): Red
- Created new icons for: commercial airliner, helicopter, cargo aircraft, general aviation, military fighter, ground vehicle
- Updated legend to reflect new weight-based categories
- Modified getAircraftColor() to assign colors based on aircraft category/weight

Closes #17

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

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

assets/static/icons/military.svg

@@ -1,7 +1,27 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <svg width="32" height="32" viewBox="0 0 32 32" xmlns="http://www.w3.org/2000/svg">
   <g transform="translate(16,16)">
-    <!-- Swept-wing fighter jet shape -->
-    <path d="M0,-12 L-4,2 L-8,8 L-2,6 L0,12 L2,6 L8,8 L4,2 Z" fill="currentColor"/>
+    <!-- Fighter jet with delta wings -->
+    <!-- Fuselage -->
+    <path d="M0,-14 L-0.8,-11 L-0.8,8 L0,10 L0.8,8 L0.8,-11 Z" fill="currentColor"/>
+    <!-- Delta wings (swept back aggressively) -->
+    <path d="M-0.8,2 L-10,8 L-9,9 L-0.8,5 Z" fill="currentColor"/>
+    <path d="M0.8,2 L10,8 L9,9 L0.8,5 Z" fill="currentColor"/>
+    <!-- Canards (small forward wings) -->
+    <path d="M-0.5,-4 L-3,-3 L-3,-2 L-0.5,-3 Z" fill="currentColor"/>
+    <path d="M0.5,-4 L3,-3 L3,-2 L0.5,-3 Z" fill="currentColor"/>
+    <!-- Vertical stabilizers (twin tails) -->
+    <path d="M-1,6 L-1.5,6 L-2.5,10 L-1,10 Z" fill="currentColor"/>
+    <path d="M1,6 L1.5,6 L2.5,10 L1,10 Z" fill="currentColor"/>
+    <!-- Nose cone (pointed) -->
+    <path d="M0,-14 L-0.8,-11 L0,-10 L0.8,-11 Z" fill="currentColor"/>
+    <!-- Air intakes -->
+    <rect x="-1.5" y="-2" width="0.7" height="3" fill="currentColor" opacity="0.7"/>
+    <rect x="0.8" y="-2" width="0.7" height="3" fill="currentColor" opacity="0.7"/>
+    <!-- Weapons hardpoints -->
+    <rect x="-5" y="6" width="0.5" height="2" fill="currentColor"/>
+    <rect x="4.5" y="6" width="0.5" height="2" fill="currentColor"/>
+    <!-- Exhaust nozzle -->
+    <ellipse cx="0" cy="9" rx="0.8" ry="1.5" fill="currentColor" opacity="0.8"/>
   </g>
 </svg>