feat(sat): point the antenna — EasyComm II az/el rotator

EasyComm is what satellite rotator controllers agreed on, so a box that
works with SatPC32, Gpredict or Hamlib works here. Serial or TCP, and its
own settings rather than the HF rotator's: an az/el pair is a different
machine on a different port, and an operator who has both must not have
to choose.

A great many EasyComm controllers — the Arduino trackers above all —
accept commands and never say a word back. That is legal and common, so a
silent controller is not treated as a broken one: it is still driven, and
the last commanded position is reported in its place, marked as commanded
rather than read. A stuck rotator must not be able to hide behind an
order it never carried out, which is why the panel shows the antenna's
position beside the satellite's.

The 450° overlap is the reason a satellite rotator is worth having, so it
is used: a pass crossing north continues past 360 instead of unwinding
three quarters of a turn with the antenna sweeping the ground. Below the
configured elevation the mast is left alone — the numbers are right all
the way round the orbit, but a rotator that chases a satellite through
the far side of the earth spends the night turning, and a mast has a
finite number of turns in it.

frontend/src/components/SatellitePanel.tsx

@@ -52,6 +52,7 @@ type Track = {
   az: number; el: number; visible: boolean;
   radio: string; // "sat" | "downlink-only" | ""
   error: string;
+  rot_on: boolean; rot_az: number; rot_el: number; rot_live: boolean;
 };
 
 const MAP_VIEW_SAT = 'opslog.satMapView';
@@ -445,6 +446,18 @@ export function SatellitePanel({ myGrid }: { myGrid: string }) {
               {tp?.inverting && <span>{t('sat.inverting')}</span>}
               {bird?.geostationary && <span>{t('sat.geo')}</span>}
             </div>
+
+            {/* Where the antenna is, beside where the satellite is. The two
+                differing is a rotator still slewing; the two differing for a
+                long time is a rotator that is stuck, and that is worth being
+                able to see without walking outside. */}
+            {tracking?.rot_on && (
+              <div className="mt-1.5 pt-1.5 border-t border-border/60 flex items-baseline gap-2 text-[11px] tabular-nums">
+                <span className="text-muted-foreground uppercase tracking-wide text-[10px]">{t('sat.antenna')}</span>
+                <span className="font-medium">{fmtDeg(tracking.rot_az)} / {fmtDeg(tracking.rot_el)}</span>
+                {!tracking.rot_live && <span className="text-muted-foreground">{t('sat.rotCommanded')}</span>}
+              </div>
+            )}
           </div>
 
           <div className="rounded-lg border border-border bg-card flex-1 min-h-0 flex flex-col">