feat: Convert Products form to vertical tab layout

Applied VerticalTabForm to ProductFormTabbed

Changes:
1. Replaced horizontal Tabs with VerticalTabForm
2. Converted TabsContent to FormSection components
3. Removed activeTab state (scroll spy handles this)
4. Dynamic tabs based on product type
   - Simple: General, Inventory, Organization
   - Variable: General, Inventory, Variations, Organization

Benefits:
✅ Consistent layout with Coupons form
✅ Better space utilization
✅ Narrower content area (more readable)
✅ Scroll spy navigation
✅ Click to scroll to section
✅ Professional UI

Layout:
- Desktop: 250px sidebar + content area
- Sidebar: Sticky with icons
- Content: Scrollable with smooth navigation
- Mobile: Keeps original horizontal tabs (future)

Removed:
- TabsList, TabsTrigger components
- activeTab state and setActiveTab calls
- Manual tab switching on validation errors

Result:
Both Products and Coupons now use same vertical tab pattern
Forms are more professional and easier to navigate

admin-spa/src/routes/Products/partials/ProductFormTabbed.tsx

@@ -3,7 +3,7 @@ import { useQuery } from '@tanstack/react-query';
 import { api } from '@/lib/api';
 import { __ } from '@/lib/i18n';
 import { Button } from '@/components/ui/button';
-import { Tabs, TabsContent, TabsList, TabsTrigger } from '@/components/ui/tabs';
+import { VerticalTabForm, FormSection } from '@/components/VerticalTabForm';
 import { Package, DollarSign, Layers, Tag } from 'lucide-react';
 import { toast } from 'sonner';
 import { GeneralTab } from './tabs/GeneralTab';
@@ -74,7 +74,6 @@ export function ProductFormTabbed({
   const [downloadable, setDownloadable] = useState(initial?.downloadable || false);
   const [featured, setFeatured] = useState(initial?.featured || false);
   const [submitting, setSubmitting] = useState(false);
-  const [activeTab, setActiveTab] = useState('general');
 
   // Update form state when initial data changes (for edit mode)
   useEffect(() => {
@@ -124,13 +123,11 @@ export function ProductFormTabbed({
     // Validation
     if (!name.trim()) {
       toast.error(__('Product name is required'));
-      setActiveTab('general');
       return;
     }
 
     if (type === 'simple' && !regularPrice) {
       toast.error(__('Regular price is required for simple products'));
-      setActiveTab('general');
       return;
     }
 
@@ -166,32 +163,19 @@ export function ProductFormTabbed({
     }
   };
 
+  // Define tabs based on product type
+  const tabs = [
+    { id: 'general', label: __('General'), icon: <Package className="w-4 h-4" /> },
+    { id: 'inventory', label: __('Inventory'), icon: <Layers className="w-4 h-4" /> },
+    ...(type === 'variable' ? [{ id: 'variations', label: __('Variations'), icon: <Layers className="w-4 h-4" /> }] : []),
+    { id: 'organization', label: __('Organization'), icon: <Tag className="w-4 h-4" /> },
+  ];
+
   return (
     <form ref={formRef} onSubmit={handleSubmit} className={className}>
-      <Tabs value={activeTab} onValueChange={setActiveTab} className="w-full">
-        <TabsList className={`grid w-full mb-6 ${type === 'variable' ? 'grid-cols-4' : 'grid-cols-3'}`}>
-          <TabsTrigger value="general" className="flex items-center gap-2">
-            <Package className="w-4 h-4" />
-            <span className="hidden sm:inline">{__('General')}</span>
-          </TabsTrigger>
-          <TabsTrigger value="inventory" className="flex items-center gap-2">
-            <Layers className="w-4 h-4" />
-            <span className="hidden sm:inline">{__('Inventory')}</span>
-          </TabsTrigger>
-          {type === 'variable' && (
-            <TabsTrigger value="variations" className="flex items-center gap-2">
-              <Layers className="w-4 h-4" />
-              <span className="hidden sm:inline">{__('Variations')}</span>
-            </TabsTrigger>
-          )}
-          <TabsTrigger value="organization" className="flex items-center gap-2">
-            <Tag className="w-4 h-4" />
-            <span className="hidden sm:inline">{__('Organization')}</span>
-          </TabsTrigger>
-        </TabsList>
-
+      <VerticalTabForm tabs={tabs}>
         {/* General Tab */}
-        <TabsContent value="general">
+        <FormSection id="general">
           <GeneralTab
             name={name}
             setName={setName}
@@ -216,10 +200,10 @@ export function ProductFormTabbed({
             salePrice={salePrice}
             setSalePrice={setSalePrice}
           />
-        </TabsContent>
+        </FormSection>
 
         {/* Inventory Tab */}
-        <TabsContent value="inventory">
+        <FormSection id="inventory">
           <InventoryTab
             manageStock={manageStock}
             setManageStock={setManageStock}
@@ -228,10 +212,11 @@ export function ProductFormTabbed({
             stockStatus={stockStatus || 'instock'}
             setStockStatus={setStockStatus}
           />
-        </TabsContent>
+        </FormSection>
 
-        {/* Variations Tab */}
-        <TabsContent value="variations">
+        {/* Variations Tab (only for variable products) */}
+        {type === 'variable' && (
+          <FormSection id="variations">
             <VariationsTab
               attributes={attributes}
               setAttributes={setAttributes}
@@ -239,10 +224,11 @@ export function ProductFormTabbed({
               setVariations={setVariations}
               regularPrice={regularPrice}
             />
-        </TabsContent>
+          </FormSection>
+        )}
 
         {/* Organization Tab */}
-        <TabsContent value="organization">
+        <FormSection id="organization">
           <OrganizationTab
             categories={categories}
             selectedCategories={selectedCategories}
@@ -251,17 +237,21 @@ export function ProductFormTabbed({
             selectedTags={selectedTags}
             setSelectedTags={setSelectedTags}
           />
-        </TabsContent>
-      </Tabs>
+        </FormSection>
 
         {/* Submit Button */}
         {!hideSubmitButton && (
-        <div className="flex justify-end gap-3 pt-6 border-t mt-6">
+          <div className="mt-6 flex gap-3">
             <Button type="submit" disabled={submitting}>
-            {submitting ? __('Saving...') : mode === 'create' ? __('Create Product') : __('Update Product')}
+              {submitting
+                ? __('Saving...')
+                : mode === 'create'
+                ? __('Create Product')
+                : __('Update Product')}
             </Button>
           </div>
         )}
+      </VerticalTabForm>
     </form>
   );
 }