feat(items): implement initial item management system

This commit introduces the foundational structure and core features for the item management application.

Key features implemented:
- **Item Listing:** A main page displaying all items in a searchable UTable.
- **Item Creation:** An "Add Item" modal with a UForm for input and validation using Zod.
- **State Management:** A `useItemsStore` composable built with `@vueuse/core`'s `useLocalStorage` to persist item data
in the browser.
- **UI Framework:** Integrated Nuxt UI for components like tables, modals, forms, and the overall layout.
- **Application Shell:** Established a default layout with a header, navigation menu, and placeholders for Export and
History pages.
- **Project Setup:** Configured pnpm workspace, Tailwind CSS, and VSCode editor settings for an improved development
experience.

app/app.vue

@@ -1,6 +1,7 @@
 <template>
-  <div>
-    <NuxtRouteAnnouncer />
-    <NuxtWelcome />
-  </div>
+  <UApp>
+    <NuxtLayout>
+      <NuxtPage />
+    </NuxtLayout>
+  </UApp>
 </template>