Radar: switch to RainViewer (IEM blocks heavy tile use), cleaner Map tab

- /api/radar/times serves RainViewer frames (cached 2 min), IEM NEXRAD only as fallback;
  sources honour maxNativeZoom so tiles overzoom instead of going blank
- Map tab opens with radar + location dot only; wind/AQI/alerts/temp/sun/lightning are opt-in,
  readout chips follow their toggles
- Bolder location dot
- Satellite (GIBS) layer: new storage key, never persisted by storm taps, radar always draws above it

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

app/public/app-ui.css

@@ -342,3 +342,9 @@ body.map-fs #tab-unified-map { padding: 0; }
 .sticky-head { background: color-mix(in srgb, var(--paper) 96%, transparent) !important; }
 .hero-hilo { background: rgba(0, 0, 0, 0.24) !important; }
 .topbar, .bottom-nav { -webkit-backdrop-filter: blur(8px); backdrop-filter: blur(8px); }
+
+/* readout chips follow their layer toggle (author display rules would otherwise beat [hidden]) */
+#tab-unified-map .map-overlay-readouts[hidden], #tab-unified-map .map-readout-chip[hidden] { display: none !important; }
+
+/* Location dot: the one thing on the map by default, so make it unmistakable (static halo, no animation) */
+.map-location-dot { width: 20px; height: 20px; background: #2563eb; border: 3px solid #fff; border-radius: 50%; box-shadow: 0 0 0 7px rgba(37, 99, 235, 0.28), 0 2px 8px rgba(0, 0, 0, 0.55); }