Scaffold Observability Metrics feature (frontend)

What does this MR do and why?

Scaffold Observability Metrics feature (frontend)

• Add page and placeholder components

Related:

• Issue: metrics: Scaffold metrics UI (gitlab-org/opstrace/opstrace#2434 - closed)
• Backend Changes: Scaffold Observability Metrics feature (backend) (!134393 - merged)

Screenshots or screen recordings

NA

How to set up and validate locally

NA

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.