Fix TSCM sweep scan resilience and add per-device error isolation

The sweep loop's WiFi/BT/RF scan processing had unprotected
timeline_manager.add_observation() calls that could crash an entire
scan iteration, silently preventing all device events from reaching
the frontend. Additionally, scan interval timestamps were only updated
at the end of processing, causing tight retry loops on persistent errors.

- Wrap timeline observation calls in try/except for all three protocols
- Move last_*_scan timestamp updates immediately after scan completes
- Add per-device try/except so one bad device doesn't block others
- Emit sweep_progress after WiFi scan for real-time status visibility
- Log warning when WiFi scan returns 0 networks for easier diagnosis
- Add known_device and score_modifier fields to correlation engine
- Add TSCM scheduling, cases, known devices, and advanced WiFi indicators

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

static/js/modes/wifi.js

@@ -879,6 +879,7 @@ const WiFiMode = (function() {
         updateNetworkRow(network);
         updateStats();
         updateProximityRadar();
+        updateChannelChart();
 
         if (onNetworkUpdate) onNetworkUpdate(network);
     }
@@ -1420,9 +1421,15 @@ const WiFiMode = (function() {
         return Object.values(stats).filter(s => s.ap_count > 0 || [1, 6, 11, 36, 40, 44, 48, 149, 153, 157, 161, 165].includes(s.channel));
     }
 
-    function updateChannelChart(band = '2.4') {
+    function updateChannelChart(band) {
         if (typeof ChannelChart === 'undefined') return;
 
+        // Use the currently active band tab if no band specified
+        if (!band) {
+            const activeTab = elements.channelBandTabs && elements.channelBandTabs.querySelector('.channel-band-tab.active');
+            band = activeTab ? activeTab.dataset.band : '2.4';
+        }
+
         // Recalculate channel stats from networks if needed
         if (channelStats.length === 0 && networks.size > 0) {
             channelStats = calculateChannelStats();