feat(admin): implement initial admin dashboard and member management

This commit introduces the foundational structure for the admin dashboard, focusing on the member management feature.
Key additions include:

- A new page at `/admin/manage/members` to display and manage members.
- An `AddModal` component with a comprehensive form for creating new members, featuring validation with Zod and input
masking.
- A reusable `PhoneInput` component with country code selection, backed by a new `useCountries` composable and a full
country dataset.
- A custom, user-friendly global error page (`error.vue`) to handle application errors gracefully.
- Updated dashboard sidebar navigation to include the new member management section.
- Added recommended VS Code extensions and settings to improve developer experience.

.vscode/extensions.json

@@ -0,0 +1,8 @@
+{
+  "recommendations": [
+    "vue.volar",
+    "nuxtr.nuxt-vscode-extentions",
+    "bradlc.vscode-tailwindcss",
+    "esbenp.prettier-vscode"
+  ]
+}