feat(sat): Doppler tracking on the radio

The hard part of satellite tuning is not the arithmetic, it is deciding
who owns the dial. A tracker that forces both frequencies fights the
operator every time they turn the knob to follow a station across a
linear transponder; one that never touches the receiver leaves them
chasing a signal that slides nine kilohertz across a 70 cm pass.

So the operator owns the receiver and the tracker follows them. Every
second it asks the radio where the receiver actually is. Where it put it,
nothing has changed. Further than a dial-turn's tolerance, and the
operator has chosen a station: what they landed on is converted back into
a nominal frequency, and the transmitter is derived from that. Which is
the division of labour on a linear bird — the operator listens, the radio
does the sums.

Three ways to reach the radio, because a satellite pair is a shape of
operating rather than a manufacturer's feature. An IC-9700 or IC-9100 is
asked for its OWN satellite mode: it pairs main and sub, gives full
duplex, and keeps the dials linked the way its designers meant, which is
always better than an imitation built out of split. A Flex gets two
slices, A the downlink and B the uplink, created when missing, because
"slice B does not exist" is not something to make an operator fix at the
start of a ten-minute pass. Everything else gets the downlink, and is
told so — half the job announced beats half the job hidden.

What goes in the log is the NOMINAL pair. Two stations working each other
through a transponder read different numbers off their dials at the same
instant; the only figure they can both agree on is the transponder's own.
FREQ is the uplink and FREQ_RX the downlink — the one place a satellite
QSO differs from every other kind, and the reason FREQ alone cannot
describe one.

frontend/src/components/SatellitePanel.tsx

@@ -1,11 +1,12 @@
 import { useCallback, useEffect, useMemo, useRef, useState } from 'react';
 import L from 'leaflet';
 import 'leaflet/dist/leaflet.css';
-import { RefreshCw, Star, Satellite as SatIcon, ClipboardPaste } from 'lucide-react';
+import { RefreshCw, Star, Satellite as SatIcon, ClipboardPaste, Radio } from 'lucide-react';
 import {
   GetSatelliteBirds, GetSatellitePositions, GetSatellitePasses, GetSatelliteTuning,
   GetSatelliteGroundTrack, GetSatelliteTLEInfo, RefreshSatelliteTLE, AddSatelliteElements,
   GetSatSettings, SaveSatSettings,
+  StartSatelliteTracking, StopSatelliteTracking, GetSatelliteTracking,
 } from '../../wailsjs/go/main/App';
 import { EventsOn } from '../../wailsjs/runtime/runtime';
 import { Button } from '@/components/ui/button';
@@ -45,6 +46,13 @@ type Tuning = {
   ctcss: number; inverting: boolean;
   az: number; el: number; range_km: number; range_rate: number; visible: boolean;
 };
+type Track = {
+  on: boolean; name: string; transponder: string; mode: string;
+  nominal_down: number; nominal_up: number; down_hz: number; up_hz: number;
+  az: number; el: number; visible: boolean;
+  radio: string; // "sat" | "downlink-only" | ""
+  error: string;
+};
 
 const MAP_VIEW_SAT = 'opslog.satMapView';
 
@@ -76,6 +84,7 @@ export function SatellitePanel({ myGrid }: { myGrid: string }) {
   const [passes, setPasses] = useState<Pass[]>([]);
   const [tuning, setTuning] = useState<Tuning | null>(null);
   const [tle, setTle] = useState<{ count: number; age_h: number; stale: boolean; custom: number } | null>(null);
+  const [tracking, setTracking] = useState<Track | null>(null);
   const [busy, setBusy] = useState(false);
   const [err, setErr] = useState('');
   const [favs, setFavs] = useState<string[]>([]);
@@ -159,6 +168,32 @@ export function SatellitePanel({ myGrid }: { myGrid: string }) {
     return () => window.clearInterval(id);
   }, [loadPasses]);
 
+  // The tracker's own state, pushed as it moves. Polled as well, at a lazy
+  // rate, so a panel opened while tracking is already running is not blank
+  // until the next tick.
+  useEffect(() => {
+    const read = async () => {
+      try { setTracking((await GetSatelliteTracking()) as any); } catch { /* not tracking */ }
+    };
+    read();
+    const off = EventsOn('sat:track', (s: any) => setTracking(s ?? null));
+    const id = window.setInterval(read, 10_000);
+    return () => { off(); window.clearInterval(id); };
+  }, []);
+
+  const toggleTracking = async () => {
+    setErr('');
+    try {
+      if (tracking?.on) {
+        await StopSatelliteTracking();
+        setTracking(null);
+      } else {
+        await StartSatelliteTracking(sel, tpIdx);
+        setTracking((await GetSatelliteTracking()) as any);
+      }
+    } catch (e: any) { setErr(String(e?.message ?? e)); }
+  };
+
   const refreshTle = async () => {
     setBusy(true); setErr('');
     try {
@@ -336,6 +371,25 @@ export function SatellitePanel({ myGrid }: { myGrid: string }) {
             <Star className={cn('size-3.5', favs.includes(bird.name) && 'fill-warning text-warning')} />
           </Button>
         )}
+        {/* Tracking is the one button on this panel that touches the radio, so
+            it says which of the two things it is doing: holding both ends of
+            the pass, or only the receiver on a rig with one. */}
+        <Button
+          size="sm"
+          variant={tracking?.on ? 'default' : 'outline'}
+          className={cn('h-7 px-2 gap-1.5', tracking?.on && 'bg-success text-background hover:bg-success/90')}
+          onClick={toggleTracking}
+          disabled={!bird?.transponders?.length}
+          title={tracking?.on
+            ? (tracking.radio === 'sat' ? t('sat.trackingFull') : t('sat.trackingDown'))
+            : t('sat.trackTip')}
+        >
+          <Radio className="size-3.5" />
+          {tracking?.on ? t('sat.tracking') : t('sat.track')}
+        </Button>
+        {tracking?.on && tracking.radio === 'downlink-only' && (
+          <span className="text-[11px] text-warning">{t('sat.downlinkOnly')}</span>
+        )}
         <div className="flex-1" />
         <span className={cn('text-[11px] tabular-nums', tle?.stale ? 'text-warning' : 'text-muted-foreground')}>
           {tleLabel}{tle?.custom ? ` · ${t('sat.tleCustom', { n: tle.custom })}` : ''}