feat(cluster): chase switches for POTA and SOTA

An operator who does not chase parks does not want NEW POTA shouting from every
activator spot. Two switches (Settings → DX Cluster, on by default): off, the
marker is withdrawn at the display layer — applySpotDisplay, the same chokepoint
the grid, the band map and the filter read through — so the badge, the colour,
the filter chip and the reference column all go quiet together, and a new-band +
new-POTA spot reads NEW BAND alone. The facts keep being computed; only the
telling stops, so ticking the box back on needs no rescan.

frontend/src/components/BandMap.tsx

@@ -272,11 +272,11 @@ export function BandMap({ band, spots, spotStatus: spotStatusRaw, currentFreqHz,
   // nothing until the next poll happened to hand over a fresh object.
   const dispOpts = readSpotDisplayOptions();
   const spotStatus = useMemo(() => {
-    if (!dispOpts.muteWorked && !dispOpts.slotHighlight) return spotStatusRaw;
+    if (!dispOpts.muteWorked && !dispOpts.slotHighlight && dispOpts.chasePota) return spotStatusRaw;
     const out: Record<string, SpotStatusEntry> = {};
     for (const k of Object.keys(spotStatusRaw)) out[k] = applySpotDisplay(spotStatusRaw[k], dispOpts) as SpotStatusEntry;
     return out;
-  }, [spotStatusRaw, dispOpts.muteWorked, dispOpts.slotHighlight]);
+  }, [spotStatusRaw, dispOpts.muteWorked, dispOpts.slotHighlight, dispOpts.chasePota]);
   // Re-render when the operator changes their IARU region in Settings.
   const [, setRegionTick] = useState(0);
   useEffect(() => subscribeIaruRegion(() => setRegionTick((n) => n + 1)), []);