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>

app.py

@@ -91,6 +91,25 @@ def add_security_headers(response):
     return response
 
 
+# ============================================
+# CONTEXT PROCESSORS
+# ============================================
+
+@app.context_processor
+def inject_offline_settings():
+    """Inject offline settings into all templates."""
+    from utils.database import get_setting
+    return {
+        'offline_settings': {
+            'enabled': get_setting('offline.enabled', False),
+            'assets_source': get_setting('offline.assets_source', 'cdn'),
+            'fonts_source': get_setting('offline.fonts_source', 'cdn'),
+            'tile_provider': get_setting('offline.tile_provider', 'openstreetmap'),
+            'tile_server_url': get_setting('offline.tile_server_url', '')
+        }
+    }
+
+
 # ============================================
 # GLOBAL PROCESS MANAGEMENT
 # ============================================