Add proximity radar visualization and signal history heatmap

Backend:
- Add device_key.py for stable device identification (identity > public MAC > fingerprint)
- Add distance.py with DistanceEstimator class (path-loss formula, EMA smoothing, confidence scoring)
- Add ring_buffer.py for time-windowed RSSI observation storage
- Extend BTDeviceAggregate with proximity_band, estimated_distance_m, distance_confidence, rssi_ema
- Add new API endpoints: /proximity/snapshot, /heatmap/data, /devices/<key>/timeseries
- Update TSCM integration to include new proximity fields

Frontend:
- Add proximity-radar.js: SVG radar with concentric rings, device dots positioned by distance
- Add timeline-heatmap.js: RSSI history grid with time buckets and color-coded signal strength
- Update bluetooth.js to initialize and feed data to new components
- Replace zone counters with radar visualization and zone summary
- Add proximity-viz.css for component styling

Tests:
- Add test_bluetooth_proximity.py with unit tests for device key stability, EMA smoothing,
  distance estimation, band classification, and ring buffer functionality

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

utils/bluetooth/__init__.py

@@ -8,12 +8,17 @@ device aggregation, RSSI statistics, and observable heuristics.
 from .aggregator import DeviceAggregator
 from .capability_check import check_capabilities, quick_adapter_check
 from .constants import (
-    # Range bands
+    # Range bands (legacy)
     RANGE_VERY_CLOSE,
     RANGE_CLOSE,
     RANGE_NEARBY,
     RANGE_FAR,
     RANGE_UNKNOWN,
+    # Proximity bands (new)
+    PROXIMITY_IMMEDIATE,
+    PROXIMITY_NEAR,
+    PROXIMITY_FAR,
+    PROXIMITY_UNKNOWN,
     # Protocols
     PROTOCOL_BLE,
     PROTOCOL_CLASSIC,
@@ -25,8 +30,11 @@ from .constants import (
     ADDRESS_TYPE_RPA,
     ADDRESS_TYPE_NRPA,
 )
+from .device_key import generate_device_key, is_randomized_mac, extract_key_type
+from .distance import DistanceEstimator, ProximityBand, get_distance_estimator
 from .heuristics import HeuristicsEngine, evaluate_device_heuristics, evaluate_all_devices
 from .models import BTDeviceAggregate, BTObservation, ScanStatus, SystemCapabilities
+from .ring_buffer import RingBuffer, get_ring_buffer, reset_ring_buffer
 from .scanner import BluetoothScanner, get_bluetooth_scanner, reset_bluetooth_scanner
 
 __all__ = [
@@ -44,6 +52,21 @@ __all__ = [
     # Aggregator
     'DeviceAggregator',
 
+    # Device key generation
+    'generate_device_key',
+    'is_randomized_mac',
+    'extract_key_type',
+
+    # Distance estimation
+    'DistanceEstimator',
+    'ProximityBand',
+    'get_distance_estimator',
+
+    # Ring buffer
+    'RingBuffer',
+    'get_ring_buffer',
+    'reset_ring_buffer',
+
     # Heuristics
     'HeuristicsEngine',
     'evaluate_device_heuristics',
@@ -53,15 +76,25 @@ __all__ = [
     'check_capabilities',
     'quick_adapter_check',
 
-    # Constants
+    # Constants - Range bands (legacy)
     'RANGE_VERY_CLOSE',
     'RANGE_CLOSE',
     'RANGE_NEARBY',
     'RANGE_FAR',
     'RANGE_UNKNOWN',
+
+    # Constants - Proximity bands (new)
+    'PROXIMITY_IMMEDIATE',
+    'PROXIMITY_NEAR',
+    'PROXIMITY_FAR',
+    'PROXIMITY_UNKNOWN',
+
+    # Constants - Protocols
     'PROTOCOL_BLE',
     'PROTOCOL_CLASSIC',
     'PROTOCOL_AUTO',
+
+    # Constants - Address types
     'ADDRESS_TYPE_PUBLIC',
     'ADDRESS_TYPE_RANDOM',
     'ADDRESS_TYPE_RANDOM_STATIC',