Add admin control for hero podcast art image; v1.1.28

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

src/App.tsx

@@ -1119,7 +1119,7 @@ function LandingPage({ content }: { content: SiteContent }) {
         <div className="hero-art">
           <div className="art-glow" aria-hidden="true" />
           <img
-            src="/images/podcast-art.jpeg"
+            src={content.podcastArtUrl || '/images/podcast-art.jpeg'}
             alt="Verse by Verse with Nate podcast artwork"
             className="podcast-art"
           />