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/css/modes/meteor.css

@@ -471,3 +471,26 @@
         height: 40px;
     }
 }
+
+html[data-ui-tier="enhanced"] .meteor-visuals-container {
+    --ms-border: rgba(46, 125, 138, 0.22);
+    --ms-surface: linear-gradient(180deg, rgba(2, 6, 6, 0.97) 0%, rgba(1, 3, 3, 0.98) 100%);
+    --ms-accent: #2e7d8a;
+    --ms-accent-dim: rgba(46, 125, 138, 0.12);
+    background: radial-gradient(circle at 14% -18%, rgba(46, 125, 138, 0.10) 0%, rgba(46, 125, 138, 0) 38%),
+        radial-gradient(circle at 86% -26%, rgba(46, 125, 138, 0.07) 0%, rgba(46, 125, 138, 0) 36%),
+        #000202;
+}
+
+html[data-ui-tier="enhanced"] .ms-headline,
+html[data-ui-tier="enhanced"] .ms-events-panel {
+    background: rgba(2, 6, 6, 0.9);
+}
+
+html[data-ui-tier="enhanced"] .ms-events-table th {
+    background: rgba(2, 6, 6, 0.95);
+}
+
+html[data-ui-tier="enhanced"] .ms-events-table tr:hover td {
+    background: rgba(46, 125, 138, 0.04);
+}