feat: Yaesu panel — sideband on re-click, split readout, one-touch up 1/up 5

Three corrections from the operator's second pass.

The sideband gesture was wrong: I used double-click, which hides the action.
Clicking a button that is ALREADY active now flips its sideband — CW-U → CW-L →
CW-U. One button, one finger, nothing to discover.

A lit SPLIT chip does not tell an operator anything useful: it says split is on,
not where they transmit. The header now shows the TX frequency and the offset in
kHz whenever split is active.

And the offset that matters is set in one action: up 1 kHz on CW, up 5 kHz on
phone. Doing it by hand means swapping VFOs, retuning and swapping back — exactly
the fumbling a panel exists to remove. Both are offered rather than picked from
the mode, because which one is idiomatic is the operator's call, and the button
turns split on at the same time.

The offset is measured from the RECEIVE frequency and written to the VFO we are
not listening on, so it stays correct when the operator works on VFO B, where the
roles are mirrored.

frontend/src/lib/i18n.tsx

@@ -106,7 +106,7 @@ const en: Dict = {
   'settings.pane.map1': 'Map — great-circle + beam', 'settings.pane.map2': 'Map — locator (street)',
   'settings.pane.cluster': 'Cluster spots', 'settings.pane.worked': 'Worked before',
   'settings.pane.recent': 'Recent QSOs', 'settings.pane.netcontrol': 'Net control',
-  'settings.pane.flex': 'FlexRadio controls', 'settings.pane.icom': 'Icom console', 'settings.pane.yaesu': 'Yaesu console', 'yaesu.notConnected': 'Yaesu CAT not connected', 'yaesu.meters': 'Meters', 'yaesu.bandMode': 'Band & mode', 'yaesu.receive': 'Receive', 'yaesu.noiseFilter': 'Noise & filter', 'yaesu.transmit': 'Transmit', 'yaesu.refresh': 'Refresh', 'yaesu.tuneHint': 'Start an antenna-tuner cycle', 'yaesu.sToRst': 'Click to fill the RST sent', 'yaesu.sidebandHint': 'Click to select this mode, double-click to switch sideband (U/L)',
+  'settings.pane.flex': 'FlexRadio controls', 'settings.pane.icom': 'Icom console', 'settings.pane.yaesu': 'Yaesu console', 'yaesu.notConnected': 'Yaesu CAT not connected', 'yaesu.meters': 'Meters', 'yaesu.bandMode': 'Band & mode', 'yaesu.receive': 'Receive', 'yaesu.noiseFilter': 'Noise & filter', 'yaesu.transmit': 'Transmit', 'yaesu.refresh': 'Refresh', 'yaesu.tuneHint': 'Start an antenna-tuner cycle', 'yaesu.sToRst': 'Click to fill the RST sent', 'yaesu.sidebandHint': 'Click to select this mode; click again to switch sideband (U/L)', 'yaesu.splitUpHint': 'Transmit this far above the receive frequency, and turn split on', 'yaesu.txOn': 'TX',
   'theme.auto': 'Auto (system)', 'theme.light-warm': 'Warm light', 'theme.light-cool': 'Cool light',
   'theme.light-sage': 'Sage light', 'theme.dim-slate': 'Dim slate', 'theme.dark-warm': 'Warm dark',
   'theme.dark-graphite': 'Graphite dark', 'theme.high-contrast': 'High contrast',
@@ -518,7 +518,7 @@ const fr: Dict = {
   'settings.pane.map1': 'Carte — orthodromie + faisceau', 'settings.pane.map2': 'Carte — locator (rue)',
   'settings.pane.cluster': 'Spots cluster', 'settings.pane.worked': 'Déjà contactés',
   'settings.pane.recent': 'QSO récents', 'settings.pane.netcontrol': 'Gestion de net',
-  'settings.pane.flex': 'Contrôles FlexRadio', 'settings.pane.icom': 'Console Icom', 'settings.pane.yaesu': 'Console Yaesu', 'yaesu.notConnected': 'CAT Yaesu non connecté', 'yaesu.meters': 'Mesures', 'yaesu.bandMode': 'Bande et mode', 'yaesu.receive': 'Réception', 'yaesu.noiseFilter': 'Bruit et filtre', 'yaesu.transmit': 'Émission', 'yaesu.refresh': 'Actualiser', 'yaesu.tuneHint': "Lancer un cycle d'accord d'antenne", 'yaesu.sToRst': 'Cliquer pour remplir le RST envoyé', 'yaesu.sidebandHint': 'Cliquer pour choisir ce mode, double-cliquer pour changer de bande latérale (U/L)',
+  'settings.pane.flex': 'Contrôles FlexRadio', 'settings.pane.icom': 'Console Icom', 'settings.pane.yaesu': 'Console Yaesu', 'yaesu.notConnected': 'CAT Yaesu non connecté', 'yaesu.meters': 'Mesures', 'yaesu.bandMode': 'Bande et mode', 'yaesu.receive': 'Réception', 'yaesu.noiseFilter': 'Bruit et filtre', 'yaesu.transmit': 'Émission', 'yaesu.refresh': 'Actualiser', 'yaesu.tuneHint': "Lancer un cycle d'accord d'antenne", 'yaesu.sToRst': 'Cliquer pour remplir le RST envoyé', 'yaesu.sidebandHint': 'Cliquer pour choisir ce mode ; recliquer pour changer de bande latérale (U/L)', 'yaesu.splitUpHint': "Émettre à cette distance au-dessus de la fréquence de réception, et activer le split", 'yaesu.txOn': 'TX',
   'theme.auto': 'Auto (système)', 'theme.light-warm': 'Clair chaud', 'theme.light-cool': 'Clair froid',
   'theme.light-sage': 'Clair sauge', 'theme.dim-slate': 'Ardoise tamisé', 'theme.dark-warm': 'Sombre chaud',
   'theme.dark-graphite': 'Sombre graphite', 'theme.high-contrast': 'Contraste élevé',