feat(appearance): Sahara theme

Built from the three sands an operator sent: #faf6eb for panels, #e8dfca
for the page behind them, #ddd2ba for toolbars, table headers and rows.
The ordering is what makes it work — a panel reads as lifted off the page
and the log grid as settled into it, so rows stay scannable without extra
rules. Ink is a deep warm brown; pure black on sand glares.

frontend/src/lib/i18n.tsx

@@ -108,7 +108,7 @@ const en: Dict = {
   'settings.pane.recent': 'Recent QSOs', 'settings.pane.netcontrol': 'Net control',
   'settings.pane.flex': 'Flex Console', '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', 'yaesu.cw': 'CW', 'yaesu.breakInHint': 'Break-in: the rig switches to receive between characters', 'yaesu.zinHint': 'Zero-in: retune so the station you hear lands on your CW pitch',
   'theme.auto': 'Auto (system)', 'theme.light-warm': 'Warm light', 'theme.light-cool': 'Cool light',
-  'theme.light-sage': 'Sage light', 'theme.light-nordic': 'Nordic light', 'theme.dim-slate': 'Dim slate', 'theme.dark-warm': 'Warm dark',
+  'theme.light-sage': 'Sage light', 'theme.light-nordic': 'Nordic light', 'theme.sahara': 'Sahara', 'theme.dim-slate': 'Dim slate', 'theme.dark-warm': 'Warm dark',
   'theme.dark-graphite': 'Graphite dark', 'theme.dark-indigo': 'Indigo', 'theme.dark-teal': 'Ocean', 'theme.dark-plum': 'Plum', 'theme.high-contrast': 'High contrast',
   // Settings navigation (sidebar groups + section names)
   'nav.user': 'User Configuration', 'nav.software': 'Software Configuration', 'nav.hardware': 'Hardware Configuration', 'nav.lists': 'Lists',
@@ -536,7 +536,7 @@ const fr: Dict = {
   'settings.pane.recent': 'QSO récents', 'settings.pane.netcontrol': 'Gestion de net',
   'settings.pane.flex': 'Flex Console', 'settings.pane.icom': 'Icom Console', 'settings.pane.yaesu': 'Yaesu Console', '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', 'yaesu.cw': 'CW', 'yaesu.breakInHint': "Break-in : la radio repasse en réception entre les caractères", 'yaesu.zinHint': "Zéro-in : réaccorde pour que la station entendue tombe sur votre note CW",
   'theme.auto': 'Auto (système)', 'theme.light-warm': 'Clair chaud', 'theme.light-cool': 'Clair froid',
-  'theme.light-sage': 'Clair sauge', 'theme.light-nordic': 'Clair nordique', 'theme.dim-slate': 'Ardoise tamisé', 'theme.dark-warm': 'Sombre chaud',
+  'theme.light-sage': 'Clair sauge', 'theme.light-nordic': 'Clair nordique', 'theme.sahara': 'Sahara', 'theme.dim-slate': 'Ardoise tamisé', 'theme.dark-warm': 'Sombre chaud',
   'theme.dark-graphite': 'Sombre graphite', 'theme.dark-indigo': 'Indigo', 'theme.dark-teal': 'Océan', 'theme.dark-plum': 'Prune', 'theme.high-contrast': 'Contraste élevé',
   'nav.user': 'Configuration utilisateur', 'nav.software': 'Configuration logicielle', 'nav.hardware': 'Configuration matérielle', 'nav.lists': 'Listes',
   'sec.station': 'Informations station', 'sec.profiles': 'Profils', 'sec.operating': "Conditions d'opération",