chore: remove demo credentials hint from login page

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/app/(auth)/login/page.tsx

@@ -221,12 +221,6 @@ function LoginForm() {
           </p>
         </div>
 
-        {/* Demo hint */}
-        <p className="text-center text-xs mt-5" style={{ color: 'var(--text-subtle)' }}>
-          Demo: <span className="font-mono" style={{ color: 'var(--text-muted)' }}>admin@vidreview.local</span>
-          {' / '}
-          <span className="font-mono" style={{ color: 'var(--text-muted)' }}>admin123</span>
-        </p>
       </div>
 
       {/* Footer */}