Is your feature request related to a problem? Please describe.

The UI Docker images (model-registry/ui and model-registry/ui-standalone) are currently built only for the linux/amd64 architecture. This prevents users on ARM-based systems from running the UI images natively.

Describe the solution you'd like

Enable multi-architecture Docker image builds for the UI images, supporting both linux/arm64 and linux/amd64 platforms. This follows the same approach implemented for the model-registry server in PR #1790.