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)} />}

web/components/ad-recreation-board.tsx

@@ -212,7 +212,7 @@ export function AdRecreationBoard({
         </header>
 
         <div className="min-h-0 flex-1 overflow-x-auto pb-2">
-          <div className="grid h-full min-w-[1520px] grid-cols-[320px_390px_1fr_360px] gap-3">
+          <div className="grid h-full min-w-[1280px] grid-cols-[300px_360px_minmax(390px,1fr)_320px] gap-3">
             <BoardColumn
               icon={<Plus className="h-4 w-4" />}
               step="01"