feat: enhance UI components and improve user experience

- Updated Toaster position to bottom-right and added custom styles for success and error messages.
- Increased font size of the brand link in AppHeader for better visibility.
- Refactored DashboardPage and GroupResultsPage to include a Footer component for consistent layout.
- Improved LandingPage with new group input handling and enhanced user feedback for ORCID input.

frontend/src/App.jsx

@@ -24,11 +24,21 @@ export default function App() {
       </Routes>
 
       <Toaster
-        position="top-right"
+        position="bottom-right"
         richColors
         closeButton
         theme="light"
         toastOptions={{ duration: 4000 }}
+        style={{
+          /* SUCCESS — ORCID corporate green */
+          '--success-bg': '#EAF3DE',
+          '--success-border': '#C0DD97',
+          '--success-text': '#3B6D11',
+          /* ERROR — hue-0° mirror of the ORCID green (same saturation & lightness) */
+          '--error-bg': '#F3DDDD',
+          '--error-border': '#DD9797',
+          '--error-text': '#6E1111',
+        }}
       />
     </AuthProvider>
   );