feat: add getMediaInfo to executor.js using ffprobe JSON output

Exposes video stream fps/codec/resolution and container duration/size
so the proxy worker can populate asset metadata after transcoding.

services/worker/src/ffmpeg/executor.js

@@ -36,6 +36,41 @@ export const getMediaDuration = async (inputPath) => {
   return parseFloat(stdout.trim());
 };
 
+/**
+ * Return structured media metadata for an input file.
+ * Result shape:
+ *   { fps, codec, resolution, durationMs, fileSizeBytes }
+ * Any field may be null if ffprobe cannot determine it.
+ */
+export const getMediaInfo = async (inputPath) => {
+  const args = [
+    '-v', 'quiet',
+    '-print_format', 'json',
+    '-show_streams',
+    '-show_format',
+    inputPath,
+  ];
+  const { stdout } = await runFFprobe(args);
+  const info = JSON.parse(stdout);
+
+  const videoStream = (info.streams || []).find(s => s.codec_type === 'video');
+  const fmt         = info.format || {};
+
+  let fps = null;
+  if (videoStream?.r_frame_rate) {
+    const [num, den] = videoStream.r_frame_rate.split('/').map(Number);
+    if (den > 0) fps = Math.round((num / den) * 1000) / 1000;
+  }
+
+  return {
+    fps,
+    codec:          videoStream?.codec_name  || null,
+    resolution:     videoStream ? `${videoStream.width}x${videoStream.height}` : null,
+    durationMs:     fmt.duration ? Math.round(parseFloat(fmt.duration) * 1000) : null,
+    fileSizeBytes:  fmt.size     ? parseInt(fmt.size, 10)                       : null,
+  };
+};
+
 export const extractFrameAtTime = async (inputPath, outputPath, timeCode) => {
   const args = [
     '-ss', timeCode,