feat: Phase 2 - Frontend meta fields components (Level 1)

Implemented: Frontend Components for Level 1 Compatibility

Created Components:
- MetaFields.tsx - Generic meta field renderer
- useMetaFields.ts - Hook for field registry

Integrated Into:
- Orders/Edit.tsx - Meta fields after OrderForm
- Products/Edit.tsx - Meta fields after ProductForm

Features:
- Supports: text, textarea, number, date, select, checkbox
- Groups fields by section
- Zero coupling with specific plugins
- Renders any registered fields dynamically
- Read-only mode support

How It Works:
1. Backend exposes meta via API (Phase 1)
2. PHP registers fields via MetaFieldsRegistry (Phase 3 - next)
3. Fields localized to window.WooNooWMetaFields
4. useMetaFields hook reads registry
5. MetaFields component renders fields
6. User edits fields
7. Form submission includes meta
8. Backend saves via update_order_meta_data()

Result:
- Generic, reusable components
- Zero plugin-specific code
- Works with any registered fields
- Clean separation of concerns

Next: Phase 3 - PHP MetaFieldsRegistry system

admin-spa/src/routes/Products/Edit.tsx

@@ -1,4 +1,4 @@
-import React, { useRef, useEffect } from 'react';
+import React, { useRef, useEffect, useState } from 'react';
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query';
 import { useNavigate, useParams } from 'react-router-dom';
 import { api } from '@/lib/api';
@@ -11,6 +11,8 @@ import { Button } from '@/components/ui/button';
 import { ErrorCard } from '@/components/ErrorCard';
 import { getPageLoadErrorMessage } from '@/lib/errorHandling';
 import { Skeleton } from '@/components/ui/skeleton';
+import { MetaFields } from '@/components/MetaFields';
+import { useMetaFields } from '@/hooks/useMetaFields';
 
 export default function ProductEdit() {
   const { id } = useParams<{ id: string }>();
@@ -19,6 +21,10 @@ export default function ProductEdit() {
   const formRef = useRef<HTMLFormElement>(null);
   const { setPageHeader, clearPageHeader } = usePageHeader();
 
+  // Level 1 compatibility: Meta fields from plugins
+  const metaFields = useMetaFields('products');
+  const [metaData, setMetaData] = useState<Record<string, any>>({});
+
   // Hide FAB on edit product page
   useFABConfig('none');
 
@@ -48,7 +54,9 @@ export default function ProductEdit() {
   });
 
   const handleSubmit = async (data: ProductFormData) => {
-    await updateMutation.mutateAsync(data);
+    // Merge meta data with form data (Level 1 compatibility)
+    const payload = { ...data, meta: metaData };
+    await updateMutation.mutateAsync(payload);
   };
 
   // Set page header with back button and save button
@@ -95,6 +103,13 @@ export default function ProductEdit() {
 
   const product = productQ.data;
 
+  // Sync meta data from product
+  useEffect(() => {
+    if (product?.meta) {
+      setMetaData(product.meta);
+    }
+  }, [product?.meta]);
+
   return (
     <div className="space-y-4">
       <ProductForm
@@ -104,6 +119,17 @@ export default function ProductEdit() {
         formRef={formRef}
         hideSubmitButton={true}
       />
+
+      {/* Level 1 compatibility: Custom meta fields from plugins */}
+      {metaFields.length > 0 && (
+        <MetaFields
+          meta={metaData}
+          fields={metaFields}
+          onChange={(key, value) => {
+            setMetaData(prev => ({ ...prev, [key]: value }));
+          }}
+        />
+      )}
     </div>
   );
 }