Fix transponder capability overwriting aircraft type in popups

Add dedicated transponder fields to prevent Mode S decoder from overwriting
the aircraft Category field with transponder capability information.

**Problem Fixed:**
- DF11 All-Call Reply messages were setting aircraft.Category to "Enhanced Transponder"
- This overwrote the actual aircraft type (Light, Medium, Heavy, etc.) from ADS-B
- Users saw "Enhanced Transponder" instead of proper aircraft classification

**Solution:**
- Added dedicated TransponderCapability and TransponderLevel fields to Aircraft struct
- Updated JSON marshaling to include new transponder fields
- Modified decodeAllCallReply() to use dedicated fields instead of Category
- Enhanced popup display to show transponder info separately from aircraft type
- Removed Category overwriting in decodeCommD() for DF24 messages

**New Aircraft Fields:**
- TransponderCapability: Human-readable capability description
- TransponderLevel: Numeric capability level (0-7)

**Popup Display:**
- Aircraft type now shows correctly (Light, Medium, Heavy, etc.)
- Transponder capability displayed as separate "Transponder:" field when available
- Only shows transponder info when DF11 messages have been received

**Data Quality Indicators Clarification:**
- NACp: Navigation Accuracy Category - Position (0-11, higher = more accurate)
- NACv: Navigation Accuracy Category - Velocity (0-4, higher = more accurate)
- SIL: Surveillance Integrity Level (0-3, higher = more reliable)

Users now see both proper aircraft classification AND transponder capability
information without conflicts between different message types.

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

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

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

@@ -362,6 +362,10 @@ export class AircraftManager {
                     <div class="detail-row">
                         <strong>Type:</strong> ${type}
                     </div>
+                    ${aircraft.TransponderCapability ? `
+                    <div class="detail-row">
+                        <strong>Transponder:</strong> ${aircraft.TransponderCapability}
+                    </div>` : ''}
                     
                     <div class="detail-grid">
                         <div class="detail-item">