Adds a per-recorder audio offset (ms) control, applied as an ffmpeg -itsoffset
on the audio input: positive delays audio (fixes audio-ahead), negative
advances, 0 = none. Flows DB (migration 037) -> mam-api (RECORDER_FIELDS +
env AUDIO_OFFSET_MS + start body) -> capture.js (sets process.env per session)
-> capture-manager audioOffsetArgs() -> ffmpeg. UI: number field in the
recorder config modal. Verified end-to-end (setting 120 -> -itsoffset 0.1200 on
the live ffmpeg). Default 0, clamped +/-1000ms, non-destructive.
Note: this is an interim trim control; the root-cause A/V fix (Deltacast JOINED
single-slot embedded-audio extraction) is tracked separately.
641b033bf4