Fix service metrics mobile layout

[arjunkomath]

Summary

• remove the redundant metrics window-end date above the chart picker
• keep service metric summaries on one row on mobile
• make the chart mode picker span the available width on mobile

Why

The date duplicates information already visible on the chart, while the existing header layout causes the summary metrics to compete with the chart picker on narrow screens.

Validation

• pnpm exec tsc --noEmit
• git diff --check

[github-actions]

React Doctor found no new issues. 🎉

_{Reviewed by React Doctor for commit a6e8e62.}