feat(09-04): page shell, drawer wiring, skeleton helper, channels placeholder

- app/mobile/profile/page.tsx: server-component shell gated by requireAuth() + redirect('/auth/sign-in')
- ProfileSectionSkeleton.tsx: generic 3-row pulsing skeleton Card
- ProfileChannelsSectionPlaceholder.tsx: stub Channels card (Plan 05 swaps real component)
- MoreDrawer.tsx Account section: identity row wrapped in Link, new Profile & preferences row above Sign-out

app/mobile/profile/page.tsx

@@ -0,0 +1,30 @@
+// /mobile/profile (PROF-01) — gated by requireAuth(), server-rendered shell
+// hosts the four client sections.
+
+import { redirect } from 'next/navigation';
+import { requireAuth } from '@/lib/auth-utils';
+import { ProfileTimezoneSection } from '@/components/mobile/profile/ProfileTimezoneSection';
+import { ProfileThemeSection } from '@/components/mobile/profile/ProfileThemeSection';
+import { ProfileNotificationMatrix } from '@/components/mobile/profile/ProfileNotificationMatrix';
+import { ProfileChannelsSection } from '@/components/mobile/profile/ProfileChannelsSectionPlaceholder';
+
+export default async function MobileProfilePage() {
+  const { session, error } = await requireAuth();
+  // CRITICAL: requireAuth() returns NextResponse on miss — that shape is for
+  // API routes only. A Page route MUST call redirect() instead. Returning
+  // `error` from here would render a JSON 401 body as the page, which is wrong.
+  if (error || !session) {
+    redirect('/auth/sign-in');
+  }
+  return (
+    <main className="px-4 pb-safe">
+      <h1 className="text-xl font-semibold pt-4 pb-2">Profile &amp; Preferences</h1>
+      <div className="space-y-4">
+        <ProfileTimezoneSection />
+        <ProfileThemeSection />
+        <ProfileNotificationMatrix />
+        <ProfileChannelsSection />
+      </div>
+    </main>
+  );
+}