Refactor frontend components and enhance API integration

- Updated frontend-nuxt.mdc to specify usage of composables for API calls.
- Added new AuthCard and ConfirmModal components for improved UI consistency.
- Introduced UserAvatar component for user profile display, replacing previous Gravatar implementation.
- Implemented useFormSubmit composable for handling form submissions with loading and error states.
- Enhanced vitest.config.ts to include coverage reporting for composables and components.
- Removed deprecated useAdminApi and useAuth composables to streamline API interactions.
- Updated login and setup pages to utilize new components and composables for better user experience.

frontend-nuxt/vitest.config.ts

@@ -6,6 +6,12 @@ export default defineConfig({
     environment: 'happy-dom',
     include: ['**/__tests__/**/*.test.ts', '**/*.test.ts'],
     globals: true,
+    coverage: {
+      provider: 'v8',
+      reporter: ['text', 'html'],
+      include: ['composables/**/*.ts', 'components/**/*.vue', 'lib/**/*.ts'],
+      exclude: ['**/*.test.ts', '**/__tests__/**', '**/__mocks__/**'],
+    },
   },
   resolve: {
     alias: {