fix: resolve two-window hang and sweep UI/theming updates

Fix app becoming unresponsive when two browser windows are open: the
root cause was HTTP/1.1 connection pool exhaustion (6-connection limit
per origin). VoiceAlerts was opening 3 SSE streams per window by
default, so two windows produced 8 connections and permanently starved
all regular HTTP requests.

- voice-alerts.js: default all streams to false (opt-in) to stay within
  the browser connection limit; existing user preferences in localStorage
  are preserved
- routes/alerts.py: replace direct AlertManager.stream_events() with
  sse_stream_fanout so both windows receive every alert instead of
  competing for the same queue
- routes/bluetooth_v2.py: same fanout fix via subscribe_fanout_queue,
  preserving named SSE events (device_update, scan_started, etc.)

Also includes accumulated UI/theming changes: accent-cyan CSS variable
sweep across mode CSS/JS files, standalone dashboard pages, template
updates, satellite TLE data refresh, and tile provider default rename.

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

static/js/modes/wifi.js

@@ -155,25 +155,22 @@ const WiFiMode = (function() {
     // ==========================================================================
 
     function init() {
-        console.log('[WiFiMode] Initializing...');
+        // Capabilities and one-time component setup only on first call.
+        // Subsequent visits refresh scan state and re-render without redundant fetches.
+        const firstInit = capabilities === null;
 
-        // Cache DOM elements
         cacheDOM();
 
-        // Check capabilities
-        checkCapabilities();
+        if (firstInit) {
+            checkCapabilities();
+            initScanModeTabs();
+            initNetworkFilters();
+            initSortControls();
+            initHeatmap();
+        }
 
-        // Initialize components
-        initScanModeTabs();
-        initNetworkFilters();
-        initSortControls();
-        initHeatmap();
         scheduleRender({ table: true, stats: true, radar: true });
-
-        // Check if already scanning
         checkScanStatus();
-
-        console.log('[WiFiMode] Initialized');
     }
 
     // DOM element cache