[refactor] Replace PrimeVue ProgressSpinner with Lucide loader icon (#9372)

## Summary
- Replace PrimeVue `ProgressSpinner` with Lucide `loader-circle` icon in
App.vue and WorkspaceAuthGate.vue
- Use white color for loading spinner for better visibility on dark
backgrounds
- Remove `primevue/progressspinner` imports and update related test

## Changes
- **App.vue**: Replace `ProgressSpinner` with
`icon-[lucide--loader-circle]`
- **WorkspaceAuthGate.vue**: Same replacement
- **WorkspaceAuthGate.test.ts**: Remove ProgressSpinner mock, use
`.animate-spin` selector

## Review Focus
- Visual consistency of white spinner on dark background during initial
load

<img width="1596" height="1189" alt="스크린샷 2026-03-04 오후 6 28 27"
src="https://github.com/user-attachments/assets/d703db74-4123-4328-912a-45ac45cf6eeb"
/>
<img width="1680" height="1304" alt="스크린샷 2026-03-04 오후 6 28 24"
src="https://github.com/user-attachments/assets/8026d10a-7e06-4f95-849c-bc891756823c"
/>

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9372-refactor-Replace-PrimeVue-ProgressSpinner-with-Lucide-loader-icon-3196d73d3650815bb1d1d4554f7f744e)
by [Unito](https://www.unito.io)

src/platform/assets/components/AssetExportProgressDialog.vue

@@ -2,6 +2,7 @@
 import { computed, ref } from 'vue'
 import { useI18n } from 'vue-i18n'
 
+import Loader from '@/components/common/Loader.vue'
 import HoneyToast from '@/components/honeyToast/HoneyToast.vue'
 import Button from '@/components/ui/button/Button.vue'
 import type { AssetExport } from '@/stores/assetExportStore'
@@ -146,9 +147,7 @@ function closeDialog() {
                 </Button>
               </template>
               <template v-else-if="job.status === 'running'">
-                <i
-                  class="icon-[lucide--loader-circle] size-4 animate-spin text-base-foreground"
-                />
+                <Loader size="sm" class="text-base-foreground" />
                 <span class="text-xs text-base-foreground">
                   {{ progressPercent(job) }}%
                 </span>