Complete multi-source Beast format implementation

Major features implemented:
- Beast binary format parser with full Mode S/ADS-B decoding
- Multi-source data merger with intelligent signal-based fusion
- Advanced web frontend with 5 view modes (Map, Table, Stats, Coverage, 3D)
- Real-time WebSocket updates with sub-second latency
- Signal strength analysis and coverage heatmaps
- Debian packaging with systemd integration
- Production-ready deployment with security hardening

Technical highlights:
- Concurrent TCP clients with auto-reconnection
- CPR position decoding and aircraft identification
- Historical flight tracking with position trails
- Range circles and receiver location visualization
- Mobile-responsive design with professional UI
- REST API and WebSocket real-time updates
- Comprehensive build system and documentation

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

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

debian/DEBIAN/postrm

@@ -0,0 +1,31 @@
+#!/bin/bash
+set -e
+
+case "$1" in
+    purge)
+        # Remove user and group
+        if getent passwd skyview >/dev/null 2>&1; then
+            deluser --system skyview >/dev/null 2>&1 || true
+        fi
+        
+        if getent group skyview >/dev/null 2>&1; then
+            delgroup --system skyview >/dev/null 2>&1 || true
+        fi
+        
+        # Remove data directories
+        rm -rf /var/lib/skyview
+        rm -rf /var/log/skyview
+        
+        # Remove config directory if empty
+        rmdir /etc/skyview 2>/dev/null || true
+        
+        echo "SkyView has been completely removed."
+        ;;
+    
+    remove)
+        # Reload systemd after service file removal
+        systemctl daemon-reload
+        ;;
+esac
+
+exit 0