Revert "feat: remove PostHog usage telemetry entirely"

This reverts commit 6a28344. Restore the once-a-day anonymous PostHog heartbeat
and its opt-out toggle: telemetry.go (sendTelemetryHeartbeat, GetTelemetryEnabled/
SetTelemetryEnabled, PostHog host + API key), the startup goroutine, the Settings
→ General toggle + i18n keys, and the README/wiki mentions. version.go is dropped
again (appVersion moves back into telemetry.go). release.ps1 (untracked) pointed
back at telemetry.go by hand.

frontend/src/components/SettingsModal.tsx

@@ -32,6 +32,7 @@ import {
   GetDatabaseSettings, PickOpenDatabase, PickSaveDatabase, OpenDatabase, MoveDatabase, ResetDatabaseToDefault, RestartApp, CreateDatabase, RenameDatabase,
   GetMySQLSettings, SaveMySQLSettings, TestMySQLConnection, GetDBBackendStatus,
   GetAutostartPrograms, SaveAutostartPrograms, BrowseExecutable, LaunchAutostartProgram,
+  GetTelemetryEnabled, SetTelemetryEnabled,
   GetQSLDefaults, SaveQSLDefaults,
   GetExternalServices, SaveExternalServices, TestQRZUpload, TestClublogUpload, TestHRDLogUpload, TestEQSLUpload,
   GetPOTAToken, SavePOTAToken,
@@ -545,6 +546,26 @@ function AutostartPanelComponent() {
   );
 }
 
+// TelemetryToggle is a self-contained opt-out for the anonymous usage heartbeat
+// (a random install ID + version + OS, sent once a day). Real component so it
+// can own its state; embedded inside GeneralPanel.
+function TelemetryToggle() {
+  const { t } = useI18n();
+  const [on, setOn] = useState(true);
+  const [loaded, setLoaded] = useState(false);
+  useEffect(() => {
+    GetTelemetryEnabled().then((v) => setOn(!!v)).catch(() => {}).finally(() => setLoaded(true));
+  }, []);
+  return (
+    <label className="flex items-center gap-2 text-sm cursor-pointer">
+      <Checkbox checked={on} disabled={!loaded}
+        onCheckedChange={(c) => { const v = !!c; setOn(v); SetTelemetryEnabled(v).catch(() => {}); }} />
+      {t('settings.telemetry')}
+      <span className="text-xs text-muted-foreground">({t('settings.telemetryHint')})</span>
+    </label>
+  );
+}
+
 // ADIFMonitorPanel watches a list of external ADIF files (fldigi RTTY, N1MM,
 // VarAC…) and auto-imports newly appended QSOs — deliberately option-free: a
 // contact that arrives is imported and uploaded automatically like any log entry.
@@ -4673,6 +4694,8 @@ export function SettingsModal({ onClose, onSaved, initialSection, onMainPaneChan
             <Checkbox checked={checkUpdates} onCheckedChange={(c) => { const v = !!c; setCheckUpdates(v); writeUiPref('opslog.checkUpdates', v ? '1' : '0'); }} />
             {t('gen.checkUpdates')} <span className="text-xs text-muted-foreground">{t('gen.checkUpdatesHint')}</span>
           </label>
+          <TelemetryToggle />
+
           <MainViewPanes onChanged={onMainPaneChanged} flexAvailable={flexAvailable} icomAvailable={icomAvailable} />
 
           <div className="border-t border-border/60 pt-4 space-y-2">

frontend/src/lib/i18n.tsx

@@ -98,6 +98,8 @@ const en: Dict = {
   'offline.synced': '{n} QSO(s) added to the logbook',
   'offline.stillDown': 'Database still unreachable — your QSOs are safe',
   'settings.theme': 'Theme', 'settings.themeHint': 'Interface colour theme.',
+  'settings.telemetry': 'Send anonymous usage statistics',
+  'settings.telemetryHint': 'install ID + version + OS, once a day — no callsign or QSO data',
   'settings.mainView': 'Main view',
   'settings.mainViewHint': 'Choose what the Main tab shows on each side (per profile).',
   'settings.leftPane': 'Left pane', 'settings.rightPane': 'Right pane',
@@ -465,6 +467,8 @@ const fr: Dict = {
   'offline.synced': '{n} QSO ajoutés au journal',
   'offline.stillDown': 'Base toujours injoignable — tes QSO sont en sécurité',
   'settings.theme': 'Thème', 'settings.themeHint': "Thème de couleur de l'interface.",
+  'settings.telemetry': "Envoyer des statistiques d'usage anonymes",
+  'settings.telemetryHint': "ID d'installation + version + OS, une fois par jour — aucun indicatif ni donnée QSO",
   'settings.mainView': 'Vue principale',
   'settings.mainViewHint': "Choisis ce que l'onglet Principal affiche de chaque côté (par profil).",
   'settings.leftPane': 'Volet gauche', 'settings.rightPane': 'Volet droit',

frontend/wailsjs/go/main/App.d.ts

@@ -472,6 +472,8 @@ export function GetStationSettings():Promise<main.StationSettings>;
 
 export function GetStationStatus():Promise<Array<main.StationDeviceStatus>>;
 
+export function GetTelemetryEnabled():Promise<boolean>;
+
 export function GetUIPref(arg1:string):Promise<string>;
 
 export function GetUltrabeamSettings():Promise<main.UltrabeamSettings>;
@@ -876,6 +878,8 @@ export function SetDVKLabel(arg1:number,arg2:string):Promise<void>;
 
 export function SetPassphrase(arg1:string):Promise<void>;
 
+export function SetTelemetryEnabled(arg1:boolean):Promise<void>;
+
 export function SetUIPref(arg1:string,arg2:string):Promise<void>;
 
 export function SetUltrabeamDirection(arg1:number):Promise<void>;

frontend/wailsjs/go/main/App.js

@@ -898,6 +898,10 @@ export function GetStationStatus() {
   return window['go']['main']['App']['GetStationStatus']();
 }
 
+export function GetTelemetryEnabled() {
+  return window['go']['main']['App']['GetTelemetryEnabled']();
+}
+
 export function GetUIPref(arg1) {
   return window['go']['main']['App']['GetUIPref'](arg1);
 }
@@ -1706,6 +1710,10 @@ export function SetPassphrase(arg1) {
   return window['go']['main']['App']['SetPassphrase'](arg1);
 }
 
+export function SetTelemetryEnabled(arg1) {
+  return window['go']['main']['App']['SetTelemetryEnabled'](arg1);
+}
+
 export function SetUIPref(arg1, arg2) {
   return window['go']['main']['App']['SetUIPref'](arg1, arg2);
 }