feat: Implement centralized module management system

- Add ModuleRegistry for managing built-in modules (newsletter, wishlist, affiliate, subscription, licensing)
- Add ModulesController REST API for module enable/disable
- Create Modules settings page with category grouping and toggle controls
- Integrate module checks across admin-spa and customer-spa
- Add useModules hook for both SPAs to check module status
- Hide newsletter from footer builder when module disabled
- Hide wishlist features when module disabled (product cards, account menu, wishlist page)
- Protect wishlist API endpoints with module checks
- Auto-update navigation tree when modules toggled
- Clean up obsolete documentation files
- Add comprehensive documentation:
  - MODULE_SYSTEM_IMPLEMENTATION.md
  - MODULE_INTEGRATION_SUMMARY.md
  - ADDON_MODULE_INTEGRATION.md (proposal)
  - ADDON_MODULE_DESIGN_DECISIONS.md (design doc)
  - FEATURE_ROADMAP.md
  - SHIPPING_INTEGRATION.md

Module system provides:
- Centralized enable/disable for all features
- Automatic navigation updates
- Frontend/backend integration
- Foundation for addon-module unification

customer-spa/src/pages/Account/Wishlist.tsx

@@ -6,6 +6,7 @@ import { useCartStore } from '@/lib/cart/store';
 import { Button } from '@/components/ui/button';
 import { formatPrice } from '@/lib/currency';
 import { toast } from 'sonner';
+import { useModules } from '@/hooks/useModules';
 
 interface WishlistItem {
   product_id: number;
@@ -26,6 +27,32 @@ export default function Wishlist() {
   const { addItem } = useCartStore();
   const [items, setItems] = useState<WishlistItem[]>([]);
   const [loading, setLoading] = useState(true);
+  const { isEnabled, isLoading: modulesLoading } = useModules();
+
+  if (modulesLoading) {
+    return (
+      <div className="min-h-screen flex items-center justify-center">
+        <div className="animate-spin rounded-full h-8 w-8 border-b-2 border-gray-900"></div>
+      </div>
+    );
+  }
+
+  if (!isEnabled('wishlist')) {
+    return (
+      <div className="min-h-screen flex items-center justify-center px-4">
+        <div className="max-w-md w-full bg-yellow-50 border border-yellow-200 rounded-lg p-8 text-center">
+          <Heart className="h-16 w-16 text-yellow-600 mx-auto mb-4" />
+          <h2 className="text-2xl font-bold mb-2">Wishlist Not Available</h2>
+          <p className="text-gray-600 mb-6">
+            The wishlist feature is currently disabled.
+          </p>
+          <Button onClick={() => navigate('/')} className="w-full">
+            Continue Shopping
+          </Button>
+        </div>
+      </div>
+    );
+  }
 
   useEffect(() => {
     loadWishlist();

customer-spa/src/pages/Account/components/AccountLayout.tsx

@@ -1,6 +1,7 @@
 import React, { ReactNode } from 'react';
 import { Link, useLocation } from 'react-router-dom';
 import { LayoutDashboard, ShoppingBag, Download, MapPin, Heart, User, LogOut } from 'lucide-react';
+import { useModules } from '@/hooks/useModules';
 
 interface AccountLayoutProps {
   children: ReactNode;
@@ -9,6 +10,7 @@ interface AccountLayoutProps {
 export function AccountLayout({ children }: AccountLayoutProps) {
   const location = useLocation();
   const user = (window as any).woonoowCustomer?.user;
+  const { isEnabled } = useModules();
   const wishlistEnabled = (window as any).woonoowCustomer?.settings?.wishlist_enabled !== false;
   
   const allMenuItems = [
@@ -20,9 +22,9 @@ export function AccountLayout({ children }: AccountLayoutProps) {
     { id: 'account-details', label: 'Account Details', path: '/my-account/account-details', icon: User },
   ];
   
-  // Filter out wishlist if disabled
+  // Filter out wishlist if module disabled or settings disabled
   const menuItems = allMenuItems.filter(item => 
-    item.id !== 'wishlist' || wishlistEnabled
+    item.id !== 'wishlist' || (isEnabled('wishlist') && wishlistEnabled)
   );
 
   const handleLogout = () => {

customer-spa/src/pages/Product/index.tsx

@@ -5,6 +5,7 @@ import { apiClient } from '@/lib/api/client';
 import { useCartStore } from '@/lib/cart/store';
 import { useProductSettings } from '@/hooks/useAppearanceSettings';
 import { useWishlist } from '@/hooks/useWishlist';
+import { useModules } from '@/hooks/useModules';
 import { Button } from '@/components/ui/button';
 import Container from '@/components/Layout/Container';
 import { ProductCard } from '@/components/ProductCard';
@@ -25,6 +26,7 @@ export default function Product() {
   const thumbnailsRef = useRef<HTMLDivElement>(null);
   const { addItem } = useCartStore();
   const { isEnabled: wishlistEnabled, isInWishlist, toggleWishlist, isLoggedIn } = useWishlist();
+  const { isEnabled: isModuleEnabled } = useModules();
 
   // Fetch product details by slug
   const { data: product, isLoading, error } = useQuery<ProductType | null>({
@@ -487,7 +489,7 @@ export default function Product() {
                   <ShoppingCart className="h-5 w-5" />
                   Add to Cart
                 </button>
-                {wishlistEnabled && (
+                {isModuleEnabled('wishlist') && wishlistEnabled && (
                   <button 
                     onClick={() => product && toggleWishlist(product.id)}
                     className={`w-full h-14 flex items-center justify-center gap-2 rounded-xl font-semibold text-base border-2 transition-all ${