feat: the header callsign is the station switcher; clock moves to the status bar

Switching station is the frequent act and editing a profile the rare one, but
the callsign opened the settings — so changing station took four clicks and a
scroll. It is now a dropdown of every profile: pick one and it activates. The
active one is ticked and disabled, and "Manage profiles…" stays at the bottom
for the rare case.

The list reloads on every profile change, so a profile added or renamed in the
settings appears without a restart.

The UTC clock leaves the header for the status bar, next to the database: in the
header it sat beside the frequency in the same weight and competed with it for
the eye, while being something you consult rather than watch.

frontend/src/lib/i18n.tsx

@@ -40,7 +40,7 @@ const en: Dict = {
   'cwd.tipOff': 'CW decoder · click to enable (decodes RX audio in CW mode)',
   'tools.net': 'NET Control', 'tools.alerts': 'Alert management…', 'tools.contest': 'Contest mode',
   'alert.tuneHint': 'Click to tune the rig to this spot (freq + mode) and fill the call', 'alert.dismiss': 'Dismiss', 'alert.pending': '{n} recent spot alert(s) — click to view', 'alert.noneShort': 'No recent alerts', 'alert.recent': 'Recent alerts', 'alert.clear': 'Clear',
-  'menu.help': 'Help', 'help.about': 'About OpsLog', 'help.donate': '♥  Support OpsLog (donate)', 'tools.duplicates': 'Find duplicates…',
+  'menu.help': 'Help', 'prof.switchTitle': 'Switch station profile', 'prof.manage': 'Manage profiles…', 'help.about': 'About OpsLog', 'help.donate': '♥  Support OpsLog (donate)', 'tools.duplicates': 'Find duplicates…',
   'help.sendLog': 'Send log to F4BPO', 'help.sendLogBusy': 'Sending log…',
   'help.sendLogOk': 'Log sent to F4BPO — thanks, 73!', 'help.sendLogFail': 'Could not send log: {err}',
   // Duplicates modal
@@ -456,7 +456,7 @@ const fr: Dict = {
   'cwd.tipOff': 'Décodeur CW · clic pour activer (décode l’audio RX en mode CW)',
   'tools.net': 'Contrôle de NET', 'tools.alerts': 'Gestion des alertes…', 'tools.contest': 'Mode contest',
   'alert.tuneHint': 'Cliquer pour accorder la radio sur ce spot (fréq + mode) et remplir l\'indicatif', 'alert.dismiss': 'Fermer', 'alert.pending': '{n} alerte(s) de spot récente(s) — cliquer pour voir', 'alert.noneShort': 'Aucune alerte récente', 'alert.recent': 'Alertes récentes', 'alert.clear': 'Effacer',
-  'menu.help': 'Aide', 'help.about': 'À propos d\'OpsLog', 'help.donate': '♥  Soutenir OpsLog (don)', 'tools.duplicates': 'Trouver les doublons…',
+  'menu.help': 'Aide', 'prof.switchTitle': 'Changer de profil de station', 'prof.manage': 'Gérer les profils…', 'help.about': 'À propos d\'OpsLog', 'help.donate': '♥  Soutenir OpsLog (don)', 'tools.duplicates': 'Trouver les doublons…',
   'help.sendLog': 'Envoyer le journal à F4BPO', 'help.sendLogBusy': 'Envoi du journal…',
   'help.sendLogOk': 'Journal envoyé à F4BPO — merci, 73 !', 'help.sendLogFail': 'Échec de l\'envoi du journal : {err}',
   'dup.title': 'Trouver les doublons', 'dup.scanning': 'Analyse du journal…', 'dup.none': 'Aucun doublon trouvé. 🎉',