feat(sat): follow the azimuth only

A satellite tracker that insists on an elevation motor is a tracker switched off
for nearly everybody. A pass at the edge of the footprint — which is most of
them — never climbs above ten or fifteen degrees for its whole length, and a
yagi's beamwidth swallows that: the bearing alone is enough, and it is how most
stations that work satellites are actually built. The same switch rescues an
az/el station whose elevation motor has failed.

So it is an option, not a silent fallback, because it does cost something: a
bird straight overhead is a moving azimuth and a bearing that means nothing, and
whether to accept that is the operator's call. With it on, any rotor in the list
can be chosen — the PstRotator, the Rotator Genius, the ARCO, the tower already
turned for HF.

That works because the per-backend command dispatch moved out of the three
RotatorGoTo/Stop/Heading methods into linkGoTo/linkStop/linkHeading, so the
satellite tracker drives any of the seven backends through the same code the
compass uses instead of a second implementation of each. GetRotatorHeading loses
sixty lines of near-duplicate switch in the process, and a rotor with no
elevation axis now says so (HasElevation) rather than reporting a zero that
looks like a real bearing.

One trap, with a test on it: the step check compared both axes, so with the
elevation never commanded its difference stayed above the step for the whole
pass and every tick ordered the antenna to the bearing it was already on. A mast
has a finite number of turns in it.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

frontend/src/lib/i18n.tsx

@@ -605,6 +605,7 @@ const en: Dict = {
   'sat.range': 'Distance', 'sat.altitude': 'Altitude', 'sat.footprint': 'Footprint',
   'sat.tipEl': 'Elevation', 'sat.tipAz': 'Azimuth', 'sat.tipRange': 'Distance', 'sat.tipAlt': 'Altitude',
   'sat.tone': 'Tone', 'sat.toneHint': 'CTCSS on the uplink', 'sat.toneNone': 'no tone needed',
+  'sat.rotAzOnly': 'azimuth only',
   'sat.tipAos': 'Rises', 'sat.tipLos': 'Sets', 'sat.tipMaxEl': 'Peak',
   'sat.tipBelow': 'below the horizon', 'sat.tipNoPass': 'no pass in the prediction window',
   'sat.approaching': 'approaching', 'sat.receding': 'receding', 'sat.below': 'below the horizon',
@@ -628,7 +629,9 @@ const en: Dict = {
   'satset.rotor': 'Azimuth / elevation rotator',
   'satset.rotEnable': 'Point a rotator at the satellite while tracking',
   'satset.rotHint': 'Point the antenna at the satellite through one of the rotators you have already configured. It is usually a separate machine from your HF rotator, and having both is normal — an az/el mast follows the pass while the beam stays where it was.',
-  'satset.rotPick': 'Rotator', 'satset.rotPickNone': '— choose a rotator —', 'satset.rotAzOnly': 'azimuth only',
+  'satset.rotPick': 'Rotator', 'satset.rotPickNone': '— choose a rotator —',
+  'satset.rotAzOnly': 'Follow the azimuth only', 'satset.rotAzOnlyTag': 'azimuth only',
+  'satset.rotAzOnlyHint': 'For a station with an ordinary azimuth rotator and no elevation motor. A pass at the edge of the footprint stays between the horizon and about 15° for its whole length, and a beam’s beamwidth covers that — so the bearing alone works. What you give up is the high passes, where a satellite overhead has a bearing that means nothing. With this on, any rotator can be chosen above.',
   'satset.rotNoneConfigured': 'No rotator configured yet',
   'satset.rotPickHint': 'One of the rotators from Settings ▸ Rotator. Add or change an interface there — a mast is described once, and this page only says which one follows the satellite.',
   'satset.rotNoElAtAll': 'None of your rotators has an elevation axis. Add an az/el interface in Settings ▸ Rotator — ERC-M, EasyComm, SPID Rot2Prog, or PstRotator with elevation ticked.',
@@ -1220,6 +1223,7 @@ const fr: Dict = {
   'sat.range': 'Distance', 'sat.altitude': 'Altitude', 'sat.footprint': 'Empreinte',
   'sat.tipEl': 'Élévation', 'sat.tipAz': 'Azimut', 'sat.tipRange': 'Distance', 'sat.tipAlt': 'Altitude',
   'sat.tone': 'Tonalité', 'sat.toneHint': 'CTCSS sur la montée', 'sat.toneNone': 'aucune tonalité requise',
+  'sat.rotAzOnly': 'azimut seul',
   'sat.tipAos': 'Lever', 'sat.tipLos': 'Coucher', 'sat.tipMaxEl': 'Culmination',
   'sat.tipBelow': 'sous l’horizon', 'sat.tipNoPass': 'aucun passage dans la fenêtre de prévision',
   'sat.approaching': 'se rapproche', 'sat.receding': 's’éloigne', 'sat.below': 'sous l’horizon',
@@ -1243,7 +1247,9 @@ const fr: Dict = {
   'satset.rotor': 'Rotor azimut / élévation',
   'satset.rotEnable': 'Pointer un rotor vers le satellite pendant le suivi',
   'satset.rotHint': 'Pointe l’antenne vers le satellite avec l’un des rotors déjà configurés. C’est en général une machine distincte du rotor HF, et avoir les deux est normal — le pylône azimut/élévation suit le passage pendant que la beam reste où elle était.',
-  'satset.rotPick': 'Rotor', 'satset.rotPickNone': '— choisir un rotor —', 'satset.rotAzOnly': 'azimut seul',
+  'satset.rotPick': 'Rotor', 'satset.rotPickNone': '— choisir un rotor —',
+  'satset.rotAzOnly': 'Suivre l’azimut seulement', 'satset.rotAzOnlyTag': 'azimut seul',
+  'satset.rotAzOnlyHint': 'Pour une station avec un rotor d’azimut ordinaire et sans moteur d’élévation. Un passage en bord d’empreinte reste entre l’horizon et 15° environ sur toute sa durée, et l’ouverture d’une beam couvre ça — le cap seul suffit donc. Ce qu’on perd, ce sont les passages hauts, où un satellite au zénith a un cap qui ne veut plus rien dire. Avec cette option, n’importe quel rotor peut être choisi ci-dessus.',
   'satset.rotNoneConfigured': 'Aucun rotor configuré pour le moment',
   'satset.rotPickHint': 'Un des rotors de Réglages ▸ Rotator. Ajoutez ou modifiez une interface là-bas — un pylône se décrit une seule fois, et cette page dit seulement lequel suit le satellite.',
   'satset.rotNoElAtAll': 'Aucun de vos rotors n’a d’axe d’élévation. Ajoutez une interface azimut/élévation dans Réglages ▸ Rotator — ERC-M, EasyComm, SPID Rot2Prog, ou PstRotator avec l’élévation cochée.',