chore(frontend): two eslint errors in the auth feature (MFAEnrollmentBanner, MFAPostAhaPrompt)

[alex-dembele]

Problem

npx eslint src/features/auth reports 2 errors on master, so the auth feature can't be held to a clean lint gate:

• src/features/auth/MFAEnrollmentBanner.tsx:61: react-refresh/only-export-components. The file exports a non-component next to the component, which breaks Fast Refresh for it.
• src/features/auth/MFAPostAhaPrompt.tsx:64: react-hooks/set-state-in-effect. setState is called synchronously inside an effect, which causes an extra render cascade.

Found while verifying #688; neither file was touched there.

Acceptance criteria

1. npx eslint src/features/auth reports 0 problems.
2. No rule is disabled or suppressed with a comment. The code is changed.
3. Behaviour is unchanged: the existing tests for both components still pass unmodified (mfaEnrollmentBanner*.test.tsx, mfaPostAhaPrompt.test.tsx).
4. Any non-component export moves to its own module and every import is updated.

Definition of Done

• npx tsc -b --noEmit, npx eslint src/features/auth, npx vitest run, npm run build green, output pasted.
• Live pass: the banner and the post-Aha prompt render and behave as before.
• Progress comment in the CLAUDE.md format; PR with Closes.

[alex-dembele]

claude — 2026-10-02

Done — frontend/src/features/auth/MFAEnrollmentBanner.tsx: copyFor no longer exported (no importers). frontend/src/features/auth/MFAPostAhaPrompt.tsx: the opening decision is taken while rendering; the effect keeps only the localStorage write. PR #885.
Verified — eslint auth 0 problems · tsc OK · vitest 993/993 (two runs) · build OK · live via a temporary harness: the 5 states (not eligible, Aha, Escape, cooldown, after cooldown) behave as before, no console errors.
Criteria — 1 ✅ · 2 ✅ · 3 ✅ · 4 ✅ (nothing to move: copyFor had no importers)
Next — owner reviews #885.
Blocked on — nothing