test: add unit tests for DashboardHeader component #1042

Testing Request

What tests are missing?
src/components/DashboardHeader.tsx has no unit tests. This component handles session-dependent rendering (Share Profile button visibility, public profile URL) and settings fetching.

Proposed Tests

// DashboardHeader.test.tsx
describe('DashboardHeader', () => {
  it('renders DEVTRACK brand label', () => {})
  it('renders DASHBOARD heading', () => {})
  it('does not show Share Profile when profile is private', () => {})
  it('shows Share Profile button when isPublic is true and session has githubLogin', () => {})
  it('Share Profile link points to correct /u/{username} URL', () => {})
  it('fetches user settings on mount when session exists', () => {})
  it('handles settings fetch failure gracefully', () => {})
  it('does not fetch settings when session is null', () => {})
})

Implementation Details

• Use Jest + React Testing Library (already set up in the project)
• Mock next-auth/react useSession hook
• Mock fetch for /api/user/settings
• File: src/components/__tests__/DashboardHeader.test.tsx

Acceptance Criteria

• All 8 test cases implemented
• Tests run with npm test
• 100% branch coverage for the component
• No real network calls in tests (all mocked)