Add home-built Grafana 12.3.3 container image based on Alpine 3.22
with pre-built OSS tarball from dl.grafana.com. Uses UID 472 for PVC
compatibility with the official image, standard Grafana paths, and
multi-arch support via TARGETPLATFORM detection.
Update service-versions.yaml to track 12.3.3.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>