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/models.py

@@ -407,6 +407,7 @@ class SystemCapabilities:
     has_hcitool: bool = False
     has_bluetoothctl: bool = False
     has_btmgmt: bool = False
+    has_ubertooth: bool = False
 
     # Recommended backend
     recommended_backend: str = 'none'
@@ -421,7 +422,8 @@ class SystemCapabilities:
             (self.has_dbus and self.has_bluez and len(self.adapters) > 0) or
             self.has_bleak or
             self.has_hcitool or
-            self.has_bluetoothctl
+            self.has_bluetoothctl or
+            self.has_ubertooth
         )
 
     def to_dict(self) -> dict:
@@ -442,6 +444,7 @@ class SystemCapabilities:
             'has_hcitool': self.has_hcitool,
             'has_bluetoothctl': self.has_bluetoothctl,
             'has_btmgmt': self.has_btmgmt,
+            'has_ubertooth': self.has_ubertooth,
             'preferred_backend': self.recommended_backend,  # Alias for frontend
             'recommended_backend': self.recommended_backend,
             'issues': self.issues,