fix: sharp globe rendering - HiDPI pixel ratio + NASA 4K texture

- Set renderer pixel ratio to window.devicePixelRatio for crisp
  rendering on Retina/HiDPI displays (was defaulting to 1)
- Upgraded Earth texture from low-res three-globe example (~2K)
  to NASA Black Marble 3600x1800 for sharp detail when zooming
- Added pointResolution(6) for cleaner point geometry

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

web/src/plugins/radio/RadioTab.tsx

@@ -180,7 +180,7 @@ export default function RadioTab({ data }: { data: any }) {
     const initAccent = initStyle.getPropertyValue('--accent').trim() || '#e67e22';
 
     const globe = new Globe(containerRef.current)
-      .globeImageUrl('//unpkg.com/three-globe/example/img/earth-night.jpg')
+      .globeImageUrl('//eoimages.gsfc.nasa.gov/images/imagerecords/79000/79765/dnb_land_ocean_ice.2012.3600x1800.jpg')
       .backgroundColor('rgba(0,0,0,0)')
       .atmosphereColor(`rgba(${initRgb}, 0.25)`)
       .atmosphereAltitude(0.12)
@@ -191,6 +191,7 @@ export default function RadioTab({ data }: { data: any }) {
       .pointColor(() => `rgba(${initRgb}, 0.85)`)
       .pointRadius((d: any) => Math.max(0.12, Math.min(0.45, 0.06 + (d.size ?? 1) * 0.005)))
       .pointAltitude(0.003)
+      .pointResolution(6)
       .pointLabel((d: any) =>
         `<div style="font-family:system-ui;font-size:13px;color:#fff;background:rgba(30,31,34,0.92);padding:6px 10px;border-radius:6px;border:1px solid rgba(${initRgb},0.3);pointer-events:none">` +
         `<b>${d.title}</b><br/><span style="color:#949ba4;font-size:11px">${d.country}</span></div>`
@@ -199,6 +200,9 @@ export default function RadioTab({ data }: { data: any }) {
       .width(containerRef.current.clientWidth)
       .height(containerRef.current.clientHeight);
 
+    // Sharp rendering on HiDPI/Retina displays
+    globe.renderer().setPixelRatio(window.devicePixelRatio);
+
     // Start-Position: Europa
     globe.pointOfView({ lat: 48, lng: 10, altitude: 2.0 });