Add animation keyframes for grid and shimmer effects, implement mouse position tracking for dynamic background, and create direct download API for video/audio files. Update types for download requests and responses.

lib/youtube.ts

@@ -1,6 +1,6 @@
 import { exec } from 'child_process';
 import { promisify } from 'util';
-import { writeFile, readFile, unlink, mkdir, copyFile } from 'fs/promises';
+import { readFile, unlink, mkdir, copyFile } from 'fs/promises';
 import { existsSync } from 'fs';
 import path from 'path';
 import type { VideoInfo, FormatOption, DownloadRequest, DownloadResponse } from './types';