refactor(media): add shared ffmpeg helpers

src/media/temp-files.ts

@@ -0,0 +1,12 @@
+import fs from "node:fs/promises";
+
+export async function unlinkIfExists(filePath: string | null | undefined): Promise<void> {
+  if (!filePath) {
+    return;
+  }
+  try {
+    await fs.unlink(filePath);
+  } catch {
+    // Best-effort cleanup for temp files.
+  }
+}