refactor(wizard): move onboarding wizard state into WizardProvider

Lift the onboarding wizard's open state, first-login auto-open effect, and the
wizard render itself out of App into WizardProvider. Feed, Channels, and
SettingsPanel trigger it via useWizard() instead of an onOpenWizard prop; App
and ChannelPage drop the prop plumbing. First step of S6b.3 — removing the
per-module props that block a uniform registry render. (Platform S6b.3)

frontend/src/components/SettingsPanel.tsx

@@ -11,6 +11,7 @@ import Tooltip from "./Tooltip";
 import { Section, SettingRow, Switch } from "./ui/form";
 import { type SaveState } from "./ui/DraftSaveBar";
 import { useConfirm } from "./ConfirmProvider";
+import { useWizard } from "./WizardProvider";
 
 // The Settings page edits server-persisted preferences. Each change applies locally for instant
 // preview AND auto-saves (debounced) — no draft, no Save button; a small indicator flashes the
@@ -39,16 +40,10 @@ const TABS: { id: TabId; icon: typeof Monitor }[] = [
 // 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.
-export default function SettingsPanel({
-  me,
-  prefs,
-  onOpenWizard,
-}: {
-  me: Me;
-  prefs: PrefsController;
-  onOpenWizard: () => void;
-}) {
+export default function SettingsPanel({ me, prefs }: { me: Me; prefs: PrefsController }) {
   const { t } = useTranslation();
+  // "Connect YouTube" onboarding lives in WizardProvider (the Account tab's reconnect button).
+  const { openWizard } = useWizard();
   const [tabRaw, setTab] = useAccountPersistedState(LS.settingsTab, "appearance");
   // Clamp at render so a stale/removed tab id falls back to Appearance.
   const tab: TabId = TABS.some((tabItem) => tabItem.id === tabRaw)
@@ -87,7 +82,7 @@ export default function SettingsPanel({
           <div className="flex-1 min-w-0 p-4">
             {tab === "appearance" && <Appearance prefs={prefs} />}
             {tab === "notifications" && <Notifications prefs={prefs} />}
-            {tab === "account" && <Account me={me} onOpenWizard={onOpenWizard} />}
+            {tab === "account" && <Account me={me} onOpenWizard={openWizard} />}
           </div>
         </div>