feat: cria nixpacks.toml para instalar o FFmpeg no container e chama executavel no path

nixpacks.toml

@@ -0,0 +1,2 @@
+[phases.setup]
+nixPkgs = ["...", "ffmpeg"]

server.js

@@ -490,7 +490,7 @@ app.post('/api/comics/generate-video', requireAuth, async (req, res) => {
     const totalDuration = frames.length * duration;
 
     // Comando FFmpeg: concatena as imagens, adiciona o áudio, ajusta o codec para h264/aac e encerra na duração final
-    const ffmpegCommand = `/usr/bin/ffmpeg -y -f concat -safe 0 -i "${concatFilePath}" -i "${bgMusicPath}" -c:v libx264 -pix_fmt yuv420p -c:a aac -shortest -t ${totalDuration} "${outputFilePath}"`;
+    const ffmpegCommand = `ffmpeg -y -f concat -safe 0 -i "${concatFilePath}" -i "${bgMusicPath}" -c:v libx264 -pix_fmt yuv420p -c:a aac -shortest -t ${totalDuration} "${outputFilePath}"`;
 
     console.log('[FFmpeg] Executando comando de vídeo:', ffmpegCommand);