Fix QA issues: bottom padding consistency and sign-out spacing

- dhikr, nur, upgrade: pb-20 → pb-24 on guest/loading screens for
  consistent clearance above the 64px bottom nav
- profile: add mb-4 to sign-out wrapper so it doesn't flush the nav

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/profile/page.tsx

@@ -200,7 +200,7 @@ export default function ProfilePage() {
       </div>
 
       {/* Sign Out */}
-      <div className="mx-4">
+      <div className="mx-4 mb-4">
         <button
           onClick={() => {
             if (typeof window !== 'undefined') {