Add React ESLint plugins and tighten CI lint checks

[jwm4]

Summary

The ESLint config covers TypeScript basics but is missing React-specific plugins that catch real bugs in hooks and JSX. The CI also allows lint warnings to accumulate without failing.

Current state

• ESLint with @eslint/js recommended + typescript-eslint recommended
• No React-specific lint rules
• CI runs eslint . which exits 0 on warnings, so warnings pile up (currently 2 pre-existing unused-var warnings in k8s-manifests.ts)

Suggested improvements

1. Add eslint-plugin-react-hooks — catches stale closures in useEffect dependencies and enforces Rules of Hooks. The React team considers this essential for any React project. We hit this gap in PR fix: filter unused provider keys from deploy configs #118 where a disable comment for the non-existent react-hooks/exhaustive-deps rule caused a CI failure.

2. Consider eslint-plugin-react — catches JSX issues like missing keys in lists. Less critical since TypeScript covers some of these, but commonly used.

3. Consider --max-warnings 0 in CI — fail CI on warnings so they get fixed promptly rather than accumulating. Warnings would still be non-blocking locally during development.

Context

The frontend is ~20 files (a deploy/management UI), so this is low-effort to adopt. It would have prevented the CI failure in PR #118.

This issue was filed by Claude Code under the supervision of Bill Murdock.