feat(ui): DisputeNavBadge component with role-based polling — closes #201

[spiffamani]

Summary

Implements DisputeNavBadge — a count badge on the Disputes nav item,
closing issue #201.

What's New

• useDisputeCount.ts — Polls GET /api/disputes every 5 minutes
  • ADMIN: counts all OPEN + UNDER_REVIEW disputes
  • USER/SHELTER: counts only disputes where raisedBy === currentUserId
  • Resets to 0 when user visits /disputes or /admin/disputes
  • Max display capped at 9+
• DisputeNavBadge.tsx — Badge component with aria-label for accessibility
• Navbar.tsx — Disputes nav link added with DisputeNavBadge integrated

Tasks Completed

• ADMIN sees count of OPEN + UNDER_REVIEW disputes
• USER/SHELTER sees count of their own open disputes
• Polls every 5 minutes using usePolling
• Resets count when user visits /disputes or /admin/disputes
• Max display: 9+
• Unit tests: admin sees total, user sees own, reset on visit

Test Results

✓ DisputeNavBadge (6 tests)
  ✓ renders nothing when count is 0
  ✓ admin sees total open dispute count
  ✓ user sees only their own dispute count
  ✓ displays "9+" when count exceeds 9
  ✓ resets to zero when on disputes page
  ✓ has accessible aria-label with count

Test Files  1 passed | Tests  6 passed

Checklist

• npm test — 6/6 passing
• tsc --noEmit — 0 errors
• Follows usePolling pattern from existing hooks
• Follows useRoleGuard for role detection
• Accessible — aria-label with count

[drips-wave]

Hey @spiffamani! 👋 It looks like this PR isn't linked to any issue.

If this PR is for one of the issues assigned to you as part of a Wave, please link it to ensure your contribution is tracked properly. You can do this by adding a keyword to the PR description (e.g., Closes #123), or by clicking a button below:

Issue	Title
#192	[Frontend · Dispute system UI] Create DisputeBanner component	Link to this issue
#201	[Frontend · Dispute system UI] Create DisputeNavBadge component	Link to this issue

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[amina69]

@spiffamani you have lint error