fix: use real browser navigation for login and logout in SSR mode

[yogeshchoudhary147]

Problem

loginWithRedirect used React Router's navigate() (client-side fetch) and logout used useSubmit. Both fail for auth routes because:

• /auth/login returns a 302 redirect to Auth0 — client-side fetch doesn't follow external redirects
• Both handlers set Set-Cookie headers that client-side fetch ignores
• logout requires a POST — useSubmit makes a fetch-based submission that doesn't follow Auth0's logout redirect

Fix

• loginWithRedirect now uses window.location.href to force a real browser request
• logout now creates and submits a native <form> element so the browser follows the redirect and processes cookies correctly
• Removed unused useSubmit import

[Piyush-85]

LGTM