v0.4.0

Server-side SEI telemetry and a wave of long-standing bug fixes from the
architecture audit.

Highlights

• Server-side SEI telemetry — new /Api/SeiData endpoint parses the
  per-frame HUD telemetry on the server. The browser HUD now fetches a
  small JSON payload instead of re-downloading the entire MP4 for every
  clip it plays, and the protobufjs CDN dependency is gone — the player
  now works fully offline / self-contained.

Fixes

• Failed or in-progress exports no longer surface as completed downloads:
  ffmpeg writes to a temp name that is renamed only on success, and
  partial files are cleaned up on failure.
• Deleting an event now removes it from the clip index immediately
  instead of leaving a stale entry until the next full refresh.
• Export progress broadcasts are throttled (250 ms) like refresh
  progress, instead of firing on every ffmpeg progress line.
• API error responses no longer leak raw exception text.
• ClipsService is now a proper singleton — the ffprobe concurrency
  gate is app-wide as intended.
• HUD throttle-pedal heuristic unified across renderers (live playback
  and export previously disagreed), and the export HUD no longer
  re-inflates genuinely low pedal values to 100 %.

Compatibility

No DB migration required; API and client remain backward compatible.
Clips without embedded SEI telemetry (pre-2026 firmware) behave as
before — the HUD simply stays hidden.