refactor: switch ad workflow to horizontal kanban

web/app/page.tsx

@@ -1007,7 +1007,7 @@ export default function Home() {
       <div className="canvas-bg" />
       <main className="relative flex h-screen w-screen overflow-hidden">
         <AdRecreationBoard data={nodeData} onGenerateVideo={handleQuickGenerateVideo} />
-        <div className="absolute right-4 top-4 z-30 pointer-events-auto">
+        <div className="absolute bottom-4 right-4 z-30 pointer-events-auto">
           <ThemeToggle />
         </div>
         {clientReady && <AudioStrip job={audioStripJob} open={!!audioStripJob} onClose={() => setAudioStripJobId(null)} />}