feat(desktop): optional wipe-on-close (Settings -> Sicherheit)

apps/desktop/src/components/SecurityCenter.tsx

@@ -1,5 +1,6 @@
 import { useState } from 'react';
 
+import { isWipeOnCloseEnabled, setWipeOnClose } from '../lib/memoryWipeSettings';
 import {
   changePin,
   type LegacyMigrationReport,
@@ -19,6 +20,7 @@ export function SecurityCenter({ userId }: Props) {
   const [msg, setMsg] = useState<string | null>(null);
   const [recovery, setRecovery] = useState<string | null>(null);
   const [migration, setMigration] = useState<LegacyMigrationReport | null>(null);
+  const [wipeOnClose, setWipeOnCloseState] = useState<boolean>(() => isWipeOnCloseEnabled());
 
   async function handleRetryMigration() {
     setBusy(true); setMsg(null); setMigration(null);
@@ -126,6 +128,27 @@ export function SecurityCenter({ userId }: Props) {
         )}
       </section>
 
+      <section>
+        <h3 className="mb-2 text-xs font-medium uppercase tracking-wide text-fg-muted">
+          Cache beim Schließen leeren
+        </h3>
+        <p className="mb-2 text-xs text-fg-muted">
+          Beim Beenden der App werden alle entschlüsselten Caches gelöscht. Beim nächsten Start
+          musst du wieder deine PIN eingeben. Empfohlen für gemeinsam genutzte Rechner.
+        </p>
+        <label className="inline-flex cursor-pointer items-center gap-2 text-sm">
+          <input
+            type="checkbox"
+            checked={wipeOnClose}
+            onChange={(e) => {
+              setWipeOnClose(e.target.checked);
+              setWipeOnCloseState(e.target.checked);
+            }}
+          />
+          <span>Aktivieren</span>
+        </label>
+      </section>
+
       <section>
         <h3 className="mb-2 text-xs font-medium uppercase tracking-wide text-rose-400">Identität zurücksetzen</h3>
         <p className="mb-2 text-xs text-fg-muted">Erstellt einen neuen Schlüssel. Alle alten Chats werden unlesbar.</p>

apps/desktop/src/context/AuthContext.tsx

@@ -21,6 +21,7 @@ import { useTranslation } from 'react-i18next';
 
 import { ensureInstallId } from '../lib/installId';
 import { wipeLocalState } from '../lib/memoryWipe';
+import { isWipeOnCloseEnabled } from '../lib/memoryWipeSettings';
 import { setSecretStoreUser } from '../lib/secretStore';
 import { supabase } from '../lib/supabase';
 import { cachedUserKey, ensureLegacyMigrated } from '../lib/userIdentity';
@@ -195,6 +196,18 @@ export function AuthProvider({ children }: { children: ReactNode }) {
     void registerWebPush(installId);
   }, [session]);
 
+  // Wipe-on-close: register a handler the main process pings on `before-quit`
+  // when the user has enabled the Settings → Sicherheit toggle. No-op outside
+  // Electron (web build has no preload bridge) or when the toggle is off.
+  useEffect(() => {
+    if (typeof window.electronAPI?.onWipeBeforeQuit !== 'function') return;
+    const unsub = window.electronAPI.onWipeBeforeQuit(async () => {
+      if (!isWipeOnCloseEnabled()) return;
+      await wipeLocalState(session?.user.id ?? null);
+    });
+    return unsub;
+  }, [session?.user.id]);
+
   // Auto online/offline transition.
   //
   // - On mount with a session whose last persisted state is `offline`, flip

apps/desktop/src/lib/memoryWipe.ts

@@ -15,6 +15,7 @@ const PRESERVE_LOCAL_STORAGE = new Set([
   'chatapp.theme',
   'chatapp.locale',
   'chatapp.installId',
+  'chatapp.wipeOnClose.v1',
   'i18nextLng',
 ]);
 

apps/desktop/src/lib/memoryWipeSettings.ts

@@ -0,0 +1,24 @@
+// Persisted toggle for the "wipe local caches on app close" feature.
+// Read by SecurityCenter (UI) and AuthContext (renderer-side IPC handler).
+//
+// Stored in localStorage so the preference survives sessions without
+// touching the secret-store or SQLite. The key is on the preserve
+// whitelist in lib/memoryWipe.ts so a sign-out wipe (or a closing wipe)
+// doesn't blow away the user's own preference.
+const KEY = 'chatapp.wipeOnClose.v1';
+
+export function isWipeOnCloseEnabled(): boolean {
+  try {
+    return window.localStorage.getItem(KEY) === '1';
+  } catch {
+    return false;
+  }
+}
+
+export function setWipeOnClose(enabled: boolean): void {
+  try {
+    window.localStorage.setItem(KEY, enabled ? '1' : '0');
+  } catch {
+    /* ignored */
+  }
+}