feat(spa): add wishlist functionality with localStorage and UI integration

apps/spa/src/store/wishlistStore.ts

@@ -0,0 +1,33 @@
+import { create } from 'zustand'
+import { persist } from 'zustand/middleware'
+import { Product } from '../types'
+
+interface WishlistState {
+  items: Product[]
+  addItem: (product: Product) => void
+  removeItem: (productId: number) => void
+  isInWishlist: (productId: number) => boolean
+}
+
+export const useWishlistStore = create<WishlistState>()(
+  persist(
+    (set, get) => ({
+      items: [],
+      addItem: (product) => {
+        const { items } = get()
+        if (!items.find(item => item.id === product.id)) {
+          set({ items: [...items, product] })
+        }
+      },
+      removeItem: (productId) => {
+        set({ items: get().items.filter(item => item.id !== productId) })
+      },
+      isInWishlist: (productId) => {
+        return get().items.some(item => item.id === productId)
+      }
+    }),
+    {
+      name: 'homaroma-wishlist',
+    }
+  )
+)