feat: Add Meshtastic, Ubertooth, and Offline Mode support

New Features:
- Meshtastic LoRa mesh network integration
  - Real-time message streaming via SSE
  - Channel configuration with encryption
  - Node information with RSSI/SNR metrics
- Ubertooth One BLE scanner backend
  - Passive capture across all 40 BLE channels
  - Raw advertising payload access
- Offline mode with bundled assets
  - Local Leaflet, Chart.js, and fonts
  - Multiple map tile providers
  - Settings modal for configuration

Technical Changes:
- New routes: meshtastic.py, offline.py
- New utils: ubertooth_scanner.py, meshtastic.py
- New CSS/JS for meshtastic and settings
- Updated dashboard templates with conditional asset loading
- Added context processor for offline settings

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

utils/bluetooth/capability_check.py

@@ -238,6 +238,9 @@ def _check_fallback_tools(caps: SystemCapabilities) -> None:
     # Check btmgmt
     caps.has_btmgmt = shutil.which('btmgmt') is not None
 
+    # Check ubertooth tools (Ubertooth One hardware)
+    caps.has_ubertooth = shutil.which('ubertooth-btle') is not None
+
     # Check CAP_NET_ADMIN for non-root users
     if not caps.is_root:
         _check_capabilities_permission(caps)