v0.3.1

A default install pulls again. A patch for one defect with two halves:
the chart's image coordinates never matched what the release workflow
publishes, so helm install with no --set could not resolve the hub, UI,
gateway or TDP-estimator images. Nothing else changes — no schema migration,
no API or config surface.

Fixed

• A default helm install now pulls the images it is supposed to. The
  chart's image defaults never matched what the release workflow publishes, in
  two independent ways: the repositories read avuruobs/hub (Docker Hub) while
  releases push ghcr.io/avuruvision/avuru-obs-hub, and the tag defaults to
  .Chart.AppVersion — bare SemVer, no leading v — while only vX.Y.Z and
  vX.Y were ever pushed. Both are fixed: the four first-party repositories
  now point at GHCR, and the release workflow additionally publishes the bare
  X.Y.Z tag. Installs that already pass --set …repository/…tag (CI e2e,
  private-registry overlays via image.registry) are unaffected.
• Green TDP estimation had no image at all. sensor.green.estimation.image
  shipped with an empty repository and no tag default, so enabling the feature
  rendered an unusable image reference. It now defaults to the published
  avuru-obs-tdp-estimator at the chart's app version, and make version-set
  stamps that image alongside the other three.