feat: Tuner Genius XL — A/B channels, plus FlexRadio panel + Station Control cards

Push the tuner control further so it mirrors the native 4O3A app and the way the
PowerGenius XL is surfaced.

Backend (internal/tunergenius):
- Status now carries both RF channels A and B (source/mode, band, frequency,
  bound Flex nickname, per-channel bypass, antenna, PTT), the active channel,
  the C1/L/C2 relay-network positions, and the 3-way-vs-SO2R hardware variant
  (learned once from the `info` reply). Flat freq/antenna still mirror the active
  channel for the compact widget.
- New TunerGeniusActivate(ch) binding → `activate ch=N` (or `ant=N` on 3-way).

Frontend:
- New shared TunerCard, styled exactly like AmpCard (PWR/SWR meter bars,
  A/B channel selector with source+freq+antenna, Tune/Bypass/Operate). Used in
  BOTH the FlexRadio panel (its own card, like the PGXL) and Station Control.
- Docked TunerGeniusPanel widget now shows the two channels A/B with their
  source/frequency/antenna and lets you click to make one active — the missing
  A/B state the user flagged.
- i18n EN/FR for the new labels (channels, antenna, in-line/bypassed, title).

Still UNTESTED on hardware — verify the per-channel field names/units and the
activate behaviour on the real box.

frontend/src/App.tsx

@@ -24,7 +24,7 @@ import {
   GetDBConnectionInfo, GetLogbookRevision,
   GetUltrabeamStatus, SetUltrabeamDirection,
   GetAntGeniusStatus, GetAntGeniusSettings, AntGeniusActivate,
-  GetTunerGeniusStatus, GetTunerGeniusSettings, TunerGeniusAutotune, TunerGeniusSetBypass, TunerGeniusSetOperate,
+  GetTunerGeniusStatus, GetTunerGeniusSettings, TunerGeniusAutotune, TunerGeniusSetBypass, TunerGeniusSetOperate, TunerGeniusActivate,
   OpenExternalURL,
   ConnectAllClusters, DisconnectAllClusters, GetClusterStatus, SendClusterCommand,
   ListClusterServers, ClusterSpotStatuses, SendClusterSpot,
@@ -1702,6 +1702,10 @@ export default function App() {
     setTgStatus((s) => ({ ...s, operate: on }));
     TunerGeniusSetOperate(on).catch((e) => setError(String(e?.message ?? e)));
   };
+  const tgActivate = (ch: number) => {
+    setTgStatus((s) => ({ ...s, active: ch })); // optimistic
+    TunerGeniusActivate(ch).catch((e) => setError(String(e?.message ?? e)));
+  };
 
   // RX band auto-follows the TX band (only differs for cross-band work).
   useEffect(() => { setBandRx(band); }, [band]);
@@ -4705,6 +4709,7 @@ export default function App() {
                 onTune={tgTune}
                 onBypass={tgBypass}
                 onOperate={tgOperate}
+                onActivate={tgActivate}
                 onClose={() => { setShowTuner(false); writeUiPref('opslog.showTuner', '0'); }}
               />
             </div>