Fix: rename inputPlaceholderText → inputPlaceholder (correct ThemeSupa type)

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

Author: 2 people

frontend/pages/auth/signin.tsx

@@ -71,7 +71,7 @@ export default function SigninPage() {
                         inputBorderHover: '#d1d5db',
                         inputLabelText: '#374151',
                         inputText: '#111827',
-                        inputPlaceholderText: '#9ca3af',
+                        inputPlaceholder: '#9ca3af',
                         inputBackground: '#ffffff',
                         defaultButtonBackground: '#ffffff',
                         defaultButtonBackgroundHover: '#f9fafb',

frontend/pages/auth/signup.tsx

@@ -97,7 +97,7 @@ export default function SignupPage() {
                       inputBorderHover: '#d1d5db',
                       inputLabelText: '#374151',
                       inputText: '#111827',
-                      inputPlaceholderText: '#9ca3af',
+                      inputPlaceholder: '#9ca3af',
                       inputBackground: '#ffffff',
                       defaultButtonBackground: '#ffffff',
                       defaultButtonBackgroundHover: '#f9fafb',