fix(server): h264 videos failing to transcode in two-pass mode (#3053)

* set `-fps_mode` to passthrough

* updated tests

server/src/domain/media/media.service.ts

@@ -222,7 +222,8 @@ export class MediaService {
       `-acodec ${ffmpeg.targetAudioCodec}`,
       // Makes a second pass moving the moov atom to the beginning of
       // the file for improved playback speed.
-      `-movflags faststart`,
+      '-movflags faststart',
+      '-fps_mode passthrough',
     ];
 
     // video dimensions