Record the mouse path and play it back with a virtual cursor ...

- Recording: content script samples mousemove at ~25 Hz (2 px / 40 ms
  thresholds), batches it to the background every second and before
  submit; stored as reports.mouse_track (viewport + points, capped and
  decimated server-side) via a new alembic migration
- Replay: a virtual cursor (overlay arrow) walks the recorded path,
  scaled to the current viewport, dispatching synthetic mousemoves so
  JS hover handlers stay live; clicks snap the cursor to the target
- Replay errors: page-load timeout aborts with a clear message, a
  closed tab aborts, per-step failures (missing elements) are
  collected, reported in the flash and in the replay result
- Panel: "Start replay" button on recording reports talks to the
  extension through a new tiny relay content script (window messages,
  no extension-id config), with presence check and toasts for
  missing extension / no response / partial replay (en + ru)

Co-Authored-By: Claude Code <noreply@anthropic.com>