fix: use CSS-based coverage rings on scanner markers

Coverage rings now render as CSS pseudo-elements on scanner markers,
following the same floor offset positioning. Toggle .heatmap-enabled
class on map container to show/hide coverage visualization.

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

src/rf_mapper/web/static/css/style.css

@@ -978,6 +978,33 @@ body {
     background: rgba(0, 200, 255, 0.9);
 }
 
+/* Scanner coverage rings (shown when heatmap enabled) */
+.heatmap-enabled .marker-3d.center .marker-icon::before,
+.heatmap-enabled .marker-3d.peer-scanner .marker-icon::before {
+    content: '';
+    position: absolute;
+    top: 50%;
+    left: 50%;
+    transform: translate(-50%, -50%);
+    width: 120px;
+    height: 120px;
+    border-radius: 50%;
+    background: radial-gradient(circle,
+        rgba(100, 255, 100, 0.3) 0%,
+        rgba(100, 255, 100, 0.2) 25%,
+        rgba(255, 255, 100, 0.15) 50%,
+        rgba(255, 100, 100, 0.1) 75%,
+        transparent 100%
+    );
+    pointer-events: none;
+    z-index: -1;
+}
+
+.heatmap-enabled .marker-3d.center .marker-icon,
+.heatmap-enabled .marker-3d.peer-scanner .marker-icon {
+    position: relative;
+}
+
 /* Trilaterated device markers - gold border */
 .marker-3d.trilaterated .marker-icon {
     border: 2px dashed #ffd700 !important;

src/rf_mapper/web/static/js/app.js

@@ -2548,6 +2548,13 @@ function toggleHeatMap() {
     const btn = document.getElementById('btn-heatmap');
     if (btn) btn.classList.toggle('active', heatMapEnabled);
 
+    // Toggle CSS class on map container for scanner coverage rings
+    const mapContainer = document.getElementById('map-3d');
+    if (mapContainer) {
+        mapContainer.classList.toggle('heatmap-enabled', heatMapEnabled);
+    }
+
+    // Also render/remove MapLibre layers for additional visualization
     if (heatMapEnabled) {
         renderHeatMap();
     } else {
@@ -2555,95 +2562,13 @@ function toggleHeatMap() {
     }
 }
 
-// Render heat map layer on 3D map
-// Uses circle layers for scanner coverage visualization
+// Render heat map visualization
+// Coverage rings are CSS-based on scanner markers (via .heatmap-enabled class)
 async function renderHeatMap() {
-    if (!map3d || !map3dLoaded) {
-        console.log('[HeatMap] 3D map not ready');
-        return;
-    }
-
-    try {
-        const resp = await fetch('/api/heatmap/signal');
-        if (!resp.ok) return;
-
-        const data = await resp.json();
-        console.log(`[HeatMap] Loaded ${data.count} points`);
-
-        // Remove existing heat map if present
-        removeHeatMap();
-
-        // Filter to scanner positions only (weight=1.0 indicates scanners)
-        const scannerPoints = data.points.filter(p => p.weight >= 0.9);
-
-        // Add coverage circles source
-        map3d.addSource('signal-heatmap', {
-            type: 'geojson',
-            data: {
-                type: 'FeatureCollection',
-                features: scannerPoints.map(p => ({
-                    type: 'Feature',
-                    geometry: { type: 'Point', coordinates: [p.lon, p.lat] },
-                    properties: { weight: p.weight }
-                }))
-            }
-        });
-
-        // Add outer coverage ring (weak signal ~15m)
-        map3d.addLayer({
-            id: 'signal-heatmap-outer',
-            type: 'circle',
-            source: 'signal-heatmap',
-            paint: {
-                'circle-radius': 80,
-                'circle-color': 'rgba(255, 100, 100, 0.15)',
-                'circle-stroke-width': 1,
-                'circle-stroke-color': 'rgba(255, 100, 100, 0.3)'
-            }
-        });
-
-        // Add middle coverage ring (fair signal ~10m)
-        map3d.addLayer({
-            id: 'signal-heatmap-middle',
-            type: 'circle',
-            source: 'signal-heatmap',
-            paint: {
-                'circle-radius': 50,
-                'circle-color': 'rgba(255, 255, 100, 0.2)',
-                'circle-stroke-width': 1,
-                'circle-stroke-color': 'rgba(255, 255, 100, 0.4)'
-            }
-        });
-
-        // Add inner coverage ring (good signal ~5m)
-        map3d.addLayer({
-            id: 'signal-heatmap-inner',
-            type: 'circle',
-            source: 'signal-heatmap',
-            paint: {
-                'circle-radius': 25,
-                'circle-color': 'rgba(100, 255, 100, 0.25)',
-                'circle-stroke-width': 1,
-                'circle-stroke-color': 'rgba(100, 255, 100, 0.5)'
-            }
-        });
-    } catch (e) {
-        console.error('[HeatMap] Error:', e);
-    }
+    console.log('[HeatMap] Enabled - coverage rings shown around scanners');
 }
 
-// Remove heat map layer from 3D map
+// Remove heat map visualization
 function removeHeatMap() {
-    if (!map3d) return;
-
-    // Remove all heatmap layers
-    ['signal-heatmap-inner', 'signal-heatmap-middle', 'signal-heatmap-outer', 'signal-heatmap-layer'].forEach(layerId => {
-        if (map3d.getLayer(layerId)) {
-            map3d.removeLayer(layerId);
-        }
-    });
-
-    if (map3d.getSource('signal-heatmap')) {
-        map3d.removeSource('signal-heatmap');
-    }
+    console.log('[HeatMap] Disabled');
 }