Enhance FloatingGenerateBox with auto-resizing textarea and default voice selection

- Added auto-resizing functionality to the textarea in FloatingGenerateBox, improving user experience when inputting text.
- Implemented logic to set the first voice profile as default if none is selected, ensuring a smoother workflow.
- Updated StoryContent to remove hardcoded height for the generate box, simplifying layout calculations.
- Refactored StoryTrackEditor to improve background styling for better visual consistency.

app/src/components/StoriesTab/StoryContent.tsx

@@ -31,9 +31,6 @@ import { useStoryPlayback } from '@/lib/hooks/useStoryPlayback';
 import { useStoryStore } from '@/stores/storyStore';
 import { SortableStoryChatItem } from './StoryChatItem';
 
-// Height of the floating generate box plus some padding
-const GENERATE_BOX_HEIGHT = 160;
-
 export function StoryContent() {
   const selectedStoryId = useStoryStore((state) => state.selectedStoryId);
   const { data: story, isLoading } = useStory(selectedStoryId);
@@ -68,8 +65,8 @@ export function StoryContent() {
   // Track editor is shown when story has items
   const hasBottomBar = story && story.items.length > 0;
 
-  // Calculate dynamic bottom padding: track editor + generate box + gap
-  const bottomPadding = hasBottomBar ? trackEditorHeight + GENERATE_BOX_HEIGHT + 24 : 0;
+  // Calculate dynamic bottom padding: track editor + gap
+  const bottomPadding = hasBottomBar ? trackEditorHeight + 24 : 0;
 
   // Drag and drop sensors
   const sensors = useSensors(

app/src/components/StoriesTab/StoryTrackEditor.tsx

@@ -345,7 +345,7 @@ export function StoryTrackEditor({ storyId, items }: StoryTrackEditorProps) {
 
   return (
     <div className="fixed bottom-0 left-0 right-0 border-t bg-background/95 backdrop-blur supports-backdrop-filter:bg-background/60 z-50">
-      <div className="border-t bg-card overflow-hidden relative" ref={containerRef}>
+      <div className="border-t bg-background/30 backdrop-blur-2xl overflow-hidden relative" ref={containerRef}>
       {/* Resize handle at top */}
       <button
         type="button"