Fix: remove invalid backgroundPrimary/Secondary/Alternative ThemeSupa properties

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

Author: 2 people

frontend/pages/auth/signin.tsx

@@ -83,10 +83,6 @@ export default function SigninPage() {
                         messageText: '#374151',
                         messageBackground: '#f9fafb',
                         messageBorder: '#e5e7eb',
-                        // Force white background throughout
-                        backgroundPrimary: '#ffffff',
-                        backgroundSecondary: '#f9fafb',
-                        backgroundAlternative: '#ffffff',
                       },
                       radii: {
                         borderRadiusButton: '0.75rem',

frontend/pages/auth/signup.tsx

@@ -109,9 +109,6 @@ export default function SignupPage() {
                       messageText: '#374151',
                       messageBackground: '#f9fafb',
                       messageBorder: '#e5e7eb',
-                      backgroundPrimary: '#ffffff',
-                      backgroundSecondary: '#f9fafb',
-                      backgroundAlternative: '#ffffff',
                     },
                     radii: {
                       borderRadiusButton: '0.75rem',