PRISM video: remount player when URL changes so admin value replaces the default; v2.36.4

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/App.tsx

@@ -1415,6 +1415,7 @@ function LandingPage({ content }: { content: SiteContent }) {
         <div className="section-inner prism-feature">
           <div className="prism-video-shell">
             <video
+              key={content.prismVideoUrl || '/images/PRISM.mp4'}
               className="prism-video"
               controls
               playsInline