Add logout button to home page

[oveddan]

Summary

• Adds a "Log out" button in the top-right corner of the home page header
• Calls the existing /api/auth/logout endpoint and redirects to /login

Test plan

• Verify the logout button appears in the header next to the title
• Click "Log out" and confirm it redirects to the login page
• Confirm the session is cleared (visiting / redirects back to /login)

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