feat: Ctrl+Up/Down hops spot-to-spot on the Main-view band map

Add a keyNav prop to BandMap: when set (only the docked Main-view map, not the
multi-band Band Map tab), Ctrl+ArrowUp / Ctrl+ArrowDown selects the next in-band
spot above / below the rig frequency and tunes to it via the existing spot-click
handler. Higher freq is up on the map (freqToY), so Up = next higher spot.
Ignored while typing in an input. Changelog 0.21.1.

frontend/src/App.tsx

@@ -5320,6 +5320,7 @@ export default function App() {
               currentFreqHz={band && freqMhz ? Math.round(parseFloat(freqMhz) * 1_000_000) : 0}
               onSpotClick={handleSpotClick}
               onClose={() => setBandMapShown(false)}
+              keyNav
             />
           </div>
         )}

frontend/src/components/BandMap.tsx

@@ -41,6 +41,10 @@ interface Props {
   // globally from the band-map tab toolbar.
   hideDigital?: boolean;
   fitToBand?: boolean;
+  // keyNav enables Ctrl+↑ / Ctrl+↓ to hop to the next spot above / below the rig
+  // frequency (and tune to it). Only the docked Main-view band map sets this, so
+  // the multi-band Band Map tab (several maps) doesn't fight over the shortcut.
+  keyNav?: boolean;
 }
 
 const BAND_RANGES: Record<string, [number, number]> = {
@@ -153,7 +157,7 @@ const BOT_PAD = 14;    // the top-most freq label isn't clipped at y=0
 // last; ties broken by closeness to the rig freq).
 const MAX_VISIBLE_SPOTS = 30;
 
-export function BandMap({ band, spots, spotStatus, currentFreqHz, onSpotClick, onClose, side = 'right', onToggleSide, hideDigital = false, fitToBand = false }: Props) {
+export function BandMap({ band, spots, spotStatus, currentFreqHz, onSpotClick, onClose, side = 'right', onToggleSide, hideDigital = false, fitToBand = false, keyNav = false }: Props) {
   const { t } = useI18n();
   const range = BAND_RANGES[band];
   const segments = SEGMENT_COLORS[band] ?? [];
@@ -362,6 +366,38 @@ export function BandMap({ band, spots, spotStatus, currentFreqHz, onSpotClick, o
     scrollerRef.current.scrollTop = Math.max(0, y - containerH / 2);
   }
 
+  // Ctrl+↑ / Ctrl+↓ hop to the next spot above / below the rig frequency and tune
+  // to it. Higher freq is UP on the map (see freqToY), so ↑ = next higher spot.
+  // Only active on the docked Main-view map (keyNav) and ignored while typing.
+  useEffect(() => {
+    if (!keyNav) return;
+    const onKey = (e: KeyboardEvent) => {
+      if (!e.ctrlKey || e.altKey || e.metaKey) return;
+      if (e.key !== 'ArrowUp' && e.key !== 'ArrowDown') return;
+      const ae = document.activeElement as HTMLElement | null;
+      const tag = (ae?.tagName || '').toLowerCase();
+      if (tag === 'input' || tag === 'textarea' || tag === 'select' || ae?.isContentEditable) return;
+      const list = spots
+        .filter((s) => (s.band ?? '') === band && s.freq_hz > 0)
+        .slice()
+        .sort((a, b) => a.freq_hz - b.freq_hz);
+      if (!list.length) return;
+      const cur = currentFreqHz || (lo + hi) * 500; // mid-band kHz→Hz when no rig freq
+      const EPS = 50; // Hz, so we don't re-pick the spot we're already sitting on
+      let target: Spot | undefined;
+      if (e.key === 'ArrowUp') {
+        target = list.find((s) => s.freq_hz > cur + EPS);
+      } else {
+        for (let i = list.length - 1; i >= 0; i--) { if (list[i].freq_hz < cur - EPS) { target = list[i]; break; } }
+      }
+      if (!target) return;
+      e.preventDefault();
+      onSpotClick(target);
+    };
+    window.addEventListener('keydown', onKey);
+    return () => window.removeEventListener('keydown', onKey);
+  }, [keyNav, spots, band, currentFreqHz, lo, hi, onSpotClick]);
+
   const currentKHz = currentFreqHz ? currentFreqHz / 1000 : 0;
   const showRigPointer = currentKHz >= lo && currentKHz <= hi;
   const rigY = freqToY(currentKHz);