refactor: rename Product Catalog to Vendor Operations

- Rename sidebar section from "Product Catalog" to "Vendor Operations"
- Change section key from 'productCatalog' to 'vendorOps'
- Add placeholder comments for future items (Inventory, Orders, Shipping)
- Update pageSectionMap in init-alpine.js

This prepares the sidebar for expanded vendor management capabilities
including inventory, orders, and shipping management.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

static/admin/js/init-alpine.js

@@ -28,7 +28,7 @@ function data() {
   // Default state: Platform Administration open, others closed
   const defaultSections = {
     platformAdmin: true,
-    productCatalog: false,
+    vendorOps: false,
     marketplace: false,
     contentMgmt: false,
     devTools: false,
@@ -64,9 +64,10 @@ function data() {
     vendors: 'platformAdmin',
     users: 'platformAdmin',
     customers: 'platformAdmin',
-    // Product Catalog
-    'marketplace-products': 'productCatalog',
-    'vendor-products': 'productCatalog',
+    // Vendor Operations (Products, Inventory, Orders, Shipping)
+    'marketplace-products': 'vendorOps',
+    'vendor-products': 'vendorOps',
+    // Future: inventory, orders, shipping will map to 'vendorOps'
     // Marketplace
     'marketplace-letzshop': 'marketplace',
     // Content Management