feat: convert uploaded OGG to MP3 via ffmpeg

lib/convert.ts

@@ -0,0 +1,23 @@
+import { execSync } from "child_process";
+import fs from "fs";
+
+export function convertOggToMp3(inputPath: string, outputPath: string): boolean {
+  try {
+    execSync(
+      `ffmpeg -i "${inputPath}" -codec:a libmp3lame -b:a 128k -y "${outputPath}" 2>/dev/null`,
+      { timeout: 15000 }
+    );
+    return true;
+  } catch {
+    return false;
+  }
+}
+
+export function convertOggToMp3OrCopy(inputPath: string, mp3Path: string): string {
+  if (convertOggToMp3(inputPath, mp3Path)) {
+    return mp3Path;
+  }
+  // fallback: keep original OGG
+  fs.copyFileSync(inputPath, mp3Path.replace(/\.mp3$/, ".ogg"));
+  return mp3Path.replace(/\.mp3$/, ".ogg");
+}