feat: Add BT Locate and GPS modes with IRK auto-detection

New modes:
- BT Locate: SAR Bluetooth device location with GPS-tagged signal trail,
  RSSI-based proximity bands, audio alerts, and IRK auto-extraction from
  paired devices (macOS plist / Linux BlueZ)
- GPS: Real-time position tracking with live map, speed, heading, altitude,
  satellite info, and track recording via gpsd

Bug fixes:
- Fix ABBA deadlock between session lock and aggregator lock in BT Locate
- Fix bleak scan lifecycle tracking in BluetoothScanner (is_scanning property
  now cross-checks backend state)
- Fix map tile persistence when switching modes
- Use 15s max_age window for fresh detections in BT Locate poll loop

Documentation:
- Update README, FEATURES.md, USAGE.md, and GitHub Pages with new modes

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

routes/__init__.py

@@ -33,6 +33,7 @@ def register_blueprints(app):
     from .alerts import alerts_bp
     from .recordings import recordings_bp
     from .subghz import subghz_bp
+    from .bt_locate import bt_locate_bp
 
     app.register_blueprint(pager_bp)
     app.register_blueprint(sensor_bp)
@@ -65,6 +66,7 @@ def register_blueprints(app):
     app.register_blueprint(alerts_bp)  # Cross-mode alerts
     app.register_blueprint(recordings_bp)  # Session recordings
     app.register_blueprint(subghz_bp)  # SubGHz transceiver (HackRF)
+    app.register_blueprint(bt_locate_bp)  # BT Locate SAR device tracking
 
     # Initialize TSCM state with queue and lock from app
     import app as app_module