Add standalone UI to docker-compose for local development

[ederign]

Is your feature request related to a problem? Please describe.
Currently, there is no easy way to showcase the complete Model Registry feature set (UI + Model Registry + Model Catalog) without deploying to a Kubernetes cluster. Users evaluating Model Registry for standalone use cases, demos, or proofs-of-concept need a simple way to experience the full stack locally.

Describe the solution you'd like
Add the Model Registry UI service to docker-compose, enabling a single command (make compose/up/postgres) to spin up the complete stack. This allows users to:

• Explore Model Registry features without Kubernetes
• Run demos and showcases locally
• Evaluate standalone deployment scenarios
• Quickly prototype integrations