feat(desktop): wipe local crypto + caches on sign-out

apps/desktop/src/context/AuthContext.tsx

@@ -20,6 +20,7 @@ import {
 import { useTranslation } from 'react-i18next';
 
 import { ensureInstallId } from '../lib/installId';
+import { wipeLocalState } from '../lib/memoryWipe';
 import { setSecretStoreUser } from '../lib/secretStore';
 import { supabase } from '../lib/supabase';
 import { cachedUserKey, ensureLegacyMigrated } from '../lib/userIdentity';
@@ -235,11 +236,13 @@ export function AuthProvider({ children }: { children: ReactNode }) {
   }, [session, profile, refreshProfile]);
 
   const signOut = useCallback(async () => {
+    const uid = session?.user.id ?? null;
     await updateOwnProfile(supabase, { presenceState: 'offline' }).catch((err: unknown) => {
       console.warn('offline update before sign-out failed', err);
     });
     await supabaseSignOut(supabase);
-  }, []);
+    await wipeLocalState(uid);
+  }, [session]);
 
   const value = useMemo<AuthContextValue>(
     () => ({