fix(autocall): disarm the stored preference, not just the loop

Withdrawing auto-call added a runtime guard and removed every control.
The stored preference was left alone, so 'enabled: true' still sits in
localStorage on the machines that had it on -- and any build without the
guard reads it and keys the transmitter for a feature that no longer has
a switch anywhere in the interface.

loadAutoCall now switches it off and writes it back the first time it
reads it, so the disarming survives a downgrade or a reinstall. Also
drops the dead auto-call state left behind in the settings modal.

A withdrawn feature that keys a radio has to be disarmed where it is
remembered, not only where it runs.

frontend/src/components/SettingsModal.tsx

@@ -80,7 +80,6 @@ import {
 } from '@/components/ui/select';
 import { cn } from '@/lib/utils';
 import { writeUiPref } from '@/lib/uiPref';
-import { loadAutoCall, autoCallKey, type AutoCallSettings, type AutoCallCriteria } from '@/lib/autocall';
 import { getDateFormat, setDateFormat, type DateFormat } from '@/lib/dateFormat';
 import { useI18n, FlagGB, FlagFR, type Lang } from '@/lib/i18n';
 import { useTheme, CONCRETE_THEMES, type ThemeChoice } from '@/lib/theme';
@@ -1933,7 +1932,6 @@ export function SettingsModal({ onClose, onSaved, initialSection, onMainPaneChan
   // feed up or down — so the write has to go where those live.
   const [bandOpen, setBandOpen] = useState<any>({ enabled: false, bands: [], available: [] });
   // How a worked square is matched, and what counts as still wanted.
-  const [autoCall, setAutoCall] = useState<AutoCallSettings>(loadAutoCall);
   const [gridScope, setGridScope] = useState<any>({ scope: 'mix_digi', hunt: 'new', scopes: [] });
   useEffect(() => { GetGridScopeSettings().then((g) => setGridScope(g as any)).catch(() => {}); }, []);
   const saveGridScope = async (next: any) => {