Add service revision changes history

[arjunkomath]

Summary

• add an authenticated, cursor-paginated Changes tab for service revision history
• show safe configuration diffs, rollout status, and current placement server names with deleted-server fallbacks
• normalize absent CPU and memory limits to prevent recurring false pending changes
• fix dashboard/service canvas vertical overflow and clipped overview chart axes
• remove the redundant Timing heading from build logs

Safety

• validates historical revision specs before comparing them
• never returns secret values or raw revision specifications to the browser
• uses stable timestamp-and-ID cursor pagination backed by a matching database index

Validation

• Smart Review: SHIP, no blockers
• npx biome check on all changed files
• npx tsc --noEmit
• npm test (21 files, 115 tests)
• npm run build
• git diff --check

[github-actions]

React Doctor found no new issues. 🎉

_{Reviewed by React Doctor for commit e8496a8.}