fix(settings): persist the active tab across reloads

The Settings tab was local React state, so F5 always snapped back to Appearance.
Persist it in localStorage (siftlode.settingsTab), validated against the tab list.

frontend/src/components/SettingsPanel.tsx

@@ -24,6 +24,14 @@ const TABS: { id: TabId; icon: typeof Monitor }[] = [
   { id: "account", icon: User },
 ];
 
+// Persist the active tab so a reload (F5) keeps the user where they were instead of
+// snapping back to "appearance".
+const SETTINGS_TAB_KEY = "siftlode.settingsTab";
+function loadSettingsTab(): TabId {
+  const v = localStorage.getItem(SETTINGS_TAB_KEY);
+  return TABS.some((tabItem) => tabItem.id === v) ? (v as TabId) : "appearance";
+}
+
 // Settings as a page (Design B): rendered in the main content area, not an overlay. It keeps
 // the frosted `.glass` surface so it still refracts the ambient backdrop. The page title is
 // shown by the Header; the tab rail stays as in-page sub-navigation.
@@ -43,7 +51,11 @@ export default function SettingsPanel({
   onOpenWizard: () => void;
 }) {
   const { t } = useTranslation();
-  const [tab, setTab] = useState<TabId>("appearance");
+  const [tab, setTabState] = useState<TabId>(loadSettingsTab);
+  const setTab = (id: TabId) => {
+    setTabState(id);
+    localStorage.setItem(SETTINGS_TAB_KEY, id);
+  };
 
   return (
     <div className="p-4 max-w-3xl w-full mx-auto">