[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/AssetBrowserModal.vue

@@ -73,11 +73,14 @@ import LeftSidePanel from '@/components/widget/panel/LeftSidePanel.vue'
 import { useFeatureFlags } from '@/composables/useFeatureFlags'
 import AssetFilterBar from '@/platform/assets/components/AssetFilterBar.vue'
 import AssetGrid from '@/platform/assets/components/AssetGrid.vue'
+import UploadModelDialog from '@/platform/assets/components/UploadModelDialog.vue'
+import UploadModelDialogHeader from '@/platform/assets/components/UploadModelDialogHeader.vue'
 import type { AssetDisplayItem } from '@/platform/assets/composables/useAssetBrowser'
 import { useAssetBrowser } from '@/platform/assets/composables/useAssetBrowser'
 import type { AssetItem } from '@/platform/assets/schemas/assetSchema'
 import { assetService } from '@/platform/assets/services/assetService'
 import { formatCategoryLabel } from '@/platform/assets/utils/categoryLabel'
+import { useDialogStore } from '@/stores/dialogStore'
 import { useModelToNodeStore } from '@/stores/modelToNodeStore'
 import { OnCloseKey } from '@/types/widgetTypes'
 
@@ -92,6 +95,7 @@ const props = defineProps<{
 }>()
 
 const { t } = useI18n()
+const dialogStore = useDialogStore()
 
 const emit = defineEmits<{
   'asset-select': [asset: AssetDisplayItem]
@@ -189,6 +193,15 @@ const { flags } = useFeatureFlags()
 const isUploadButtonEnabled = computed(() => flags.modelUploadButtonEnabled)
 
 function handleUploadClick() {
-  // Will be implemented in the future commit
+  dialogStore.showDialog({
+    key: 'upload-model',
+    headerComponent: UploadModelDialogHeader,
+    component: UploadModelDialog,
+    props: {
+      onUploadSuccess: async () => {
+        await execute()
+      }
+    }
+  })
 }
 </script>