fix(camera): recover browser preview after permission is granted

[cn0303]

Problem

The camera preview (useCameraStream) makes a single getUserMedia attempt. On first
use that attempt can fail because:

• the page has not been granted camera permission yet (the grant is driven separately by
  useAvailableCameras' probe getUserMedia), or
• the device is briefly held right after that probe releases it (transient NotReadableError).

Because the bound deviceId doesn't change once permission lands, the hook stays stuck in the
error state until a full page reload. This is visible today on:

• Calibration → camera previews
• Recording → camera configuration previews

both showing Preview failed / No browser match on the first visit, only fixed by reloading.

Steps to reproduce

1. Reset camera permission for the site (or use a fresh incognito window).
2. Open the Calibration page and enable cameras (or open Recording's camera config).
3. Grant the camera permission when prompted.
4. The previews stay on "Preview failed" / "No browser match" until you reload the page.

Fix

• Error-aware retry. Only transient failures (NotReadableError / AbortError, i.e. the device
  is briefly held) are retried, with exponential backoff (300ms → 600ms → 1200ms → ...).
  Permanent-at-this-instant errors; permission denial (NotAllowedError), missing device
  (NotFoundError), unsatisfiable constraints (OverconstrainedError) — are not spin-retried.
• Event-driven recovery. Those non-transient cases recover when the browser fires devicechange
  which can follow a permission grant or a device-exposure change (the browser doesn't guarantee
  timing) and only while already in the error state, so a healthy stream is never torn down by an
  unrelated device change (e.g. plugging in a microphone).

The preview now recovers on its own, no reload needed. Behaviour while paused is unchanged
(stream is still released for cv2 during recording).

Testing

• Manual: cold-start permission flow on Calibration and Recording; previews come up first-try
  after granting, no reload.
• npx tsc --noEmit clean; ESLint clean on the changed file (note: the repo's full npm run lint
  already reports pre-existing errors/warnings unrelated to this change); npm run build succeeds.