[feat] Add Civitai model upload wizard (#6694)

## Summary
Adds a complete model upload workflow that allows users to import models
from Civitai URLs directly into their library.

## Changes
- **Multi-step wizard**: URL input → metadata confirmation → upload
progress
- **Components**: UploadModelDialog, UploadModelUrlInput,
UploadModelConfirmation, UploadModelProgress, UploadModelDialogHeader
- **API integration**: New assetService methods for metadata retrieval
and URL-based uploads
- **Model type management**: useModelTypes composable for fetching and
formatting available model types
- **UX improvements**: Optional validation bypass for UrlInput component
- **Localization**: 26 new i18n strings for the upload workflow

## Review Focus
- Error handling for failed uploads and metadata retrieval
- Model type detection and selection logic
- Dialog state management across multi-step workflow

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-6694-feat-Add-Civitai-model-upload-wizard-2ab6d73d36508193b3b1dd67c7cc5a09)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Claude <noreply@anthropic.com>

src/platform/assets/components/UploadModelUrlInput.vue

@@ -0,0 +1,50 @@
+<template>
+  <div class="flex flex-col gap-4">
+    <div class="flex flex-col gap-2">
+      <p class="text-sm text-muted m-0">
+        {{ $t('assetBrowser.uploadModelDescription1') }}
+      </p>
+      <ul class="list-disc space-y-1 pl-5 mt-0 text-sm text-muted">
+        <li>{{ $t('assetBrowser.uploadModelDescription2') }}</li>
+        <li>{{ $t('assetBrowser.uploadModelDescription3') }}</li>
+      </ul>
+    </div>
+
+    <div class="flex flex-col gap-2">
+      <label class="text-sm text-muted mb-0">
+        {{ $t('assetBrowser.civitaiLinkLabel') }}
+      </label>
+      <UrlInput
+        v-model="url"
+        :placeholder="$t('assetBrowser.civitaiLinkPlaceholder')"
+        :disable-validation="true"
+      />
+      <p v-if="error" class="text-xs text-error">
+        {{ error }}
+      </p>
+      <p v-else class="text-xs text-muted">
+        {{ $t('assetBrowser.civitaiLinkExample') }}
+      </p>
+    </div>
+  </div>
+</template>
+
+<script setup lang="ts">
+import { computed } from 'vue'
+
+import UrlInput from '@/components/common/UrlInput.vue'
+
+const props = defineProps<{
+  modelValue: string
+  error?: string
+}>()
+
+const emit = defineEmits<{
+  'update:modelValue': [value: string]
+}>()
+
+const url = computed({
+  get: () => props.modelValue,
+  set: (value: string) => emit('update:modelValue', value)
+})
+</script>