Restructure frontend code to allow for extensions (#4721)

# Description of Changes
Move frontend code into `core` folder and add infrastructure for
`proprietary` folder to include premium, non-OSS features

frontend/src/proprietary/components/shared/config/OverviewHeader.tsx

@@ -0,0 +1,42 @@
+import { Text, Button } from '@mantine/core';
+import { useTranslation } from 'react-i18next';
+import { useAuth } from '@app/auth/UseSession';
+import { useNavigate } from 'react-router-dom';
+
+export function OverviewHeader() {
+  const { t } = useTranslation();
+  const { signOut, user } = useAuth();
+  const navigate = useNavigate();
+
+  const handleLogout = async () => {
+    try {
+      await signOut();
+      navigate('/login');
+    } catch (error) {
+      console.error('Logout error:', error);
+    }
+  };
+
+  return (
+    <div>
+      <div style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'center', marginBottom: '0.5rem' }}>
+        <div>
+          <Text fw={600} size="lg">{t('config.overview.title', 'Application Configuration')}</Text>
+          <Text size="sm" c="dimmed">
+            {t('config.overview.description', 'Current application settings and configuration details.')}
+          </Text>
+          {user?.email && (
+            <Text size="xs" c="dimmed" mt="0.25rem">
+              Signed in as: {user.email}
+            </Text>
+          )}
+        </div>
+        {user && (
+          <Button color="red" variant="filled" onClick={handleLogout}>
+            Log out
+          </Button>
+        )}
+      </div>
+    </div>
+  );
+}