fix: Add bottom padding to main content for player clearance

App.tsx main element now has pb-24 (96px bottom padding) so the
gallery content always has breathing room above the fixed player bar.
Prevents content from sitting flush against the player controls.

frontend/src/App.tsx

@@ -164,7 +164,7 @@ function App() {
         </div>
       </header>
 
-      <main className="max-w-6xl mx-auto p-6 grid grid-cols-1 lg:grid-cols-3 gap-6">
+      <main className="max-w-6xl mx-auto p-6 pb-24 grid grid-cols-1 lg:grid-cols-3 gap-6">
         <div className="lg:col-span-1">
           <Generator onGenerate={fetchClips} />
         </div>