feat: Add WordPress button, settings navigation, and placeholder pages

admin-spa/src/routes/Settings/Shipping.tsx

@@ -0,0 +1,19 @@
+import React from 'react';
+import { __ } from '@/lib/i18n';
+
+export default function SettingsShipping() {
+  return (
+    <div>
+      <h1 className="text-2xl font-semibold mb-6">{__('Shipping Settings')}</h1>
+      <p className="text-muted-foreground mb-4">
+        {__('Configure shipping zones, methods, and rates.')}
+      </p>
+      
+      <div className="bg-muted/50 border rounded-lg p-6">
+        <p className="text-sm text-muted-foreground">
+          {__('Shipping settings interface coming soon. This will include zones, methods, and rates configuration.')}
+        </p>
+      </div>
+    </div>
+  );
+}