[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/composables/useUploadModelWizard.ts

@@ -0,0 +1,175 @@
+import type { Ref } from 'vue'
+import { computed, ref, watch } from 'vue'
+
+import { st } from '@/i18n'
+import type { AssetMetadata } from '@/platform/assets/schemas/assetSchema'
+import { assetService } from '@/platform/assets/services/assetService'
+
+interface WizardData {
+  url: string
+  metadata: AssetMetadata | null
+  name: string
+  tags: string[]
+}
+
+interface ModelTypeOption {
+  name: string
+  value: string
+}
+
+export function useUploadModelWizard(modelTypes: Ref<ModelTypeOption[]>) {
+  const currentStep = ref(1)
+  const isFetchingMetadata = ref(false)
+  const isUploading = ref(false)
+  const uploadStatus = ref<'idle' | 'uploading' | 'success' | 'error'>('idle')
+  const uploadError = ref('')
+
+  const wizardData = ref<WizardData>({
+    url: '',
+    metadata: null,
+    name: '',
+    tags: []
+  })
+
+  const selectedModelType = ref<string | undefined>(undefined)
+
+  // Clear error when URL changes
+  watch(
+    () => wizardData.value.url,
+    () => {
+      uploadError.value = ''
+    }
+  )
+
+  // Validation
+  const canFetchMetadata = computed(() => {
+    return wizardData.value.url.trim().length > 0
+  })
+
+  const canUploadModel = computed(() => {
+    return !!selectedModelType.value
+  })
+
+  function isCivitaiUrl(url: string): boolean {
+    try {
+      const hostname = new URL(url).hostname.toLowerCase()
+      return hostname === 'civitai.com' || hostname.endsWith('.civitai.com')
+    } catch {
+      return false
+    }
+  }
+
+  async function fetchMetadata() {
+    if (!canFetchMetadata.value) return
+
+    if (!isCivitaiUrl(wizardData.value.url)) {
+      uploadError.value = st(
+        'assetBrowser.onlyCivitaiUrlsSupported',
+        'Only Civitai URLs are supported'
+      )
+      return
+    }
+
+    isFetchingMetadata.value = true
+    try {
+      const metadata = await assetService.getAssetMetadata(wizardData.value.url)
+      wizardData.value.metadata = metadata
+
+      // Pre-fill name from metadata
+      wizardData.value.name = metadata.filename || metadata.name || ''
+
+      // Pre-fill model type from metadata tags if available
+      if (metadata.tags && metadata.tags.length > 0) {
+        wizardData.value.tags = metadata.tags
+        // Try to detect model type from tags
+        const typeTag = metadata.tags.find((tag) =>
+          modelTypes.value.some((type) => type.value === tag)
+        )
+        if (typeTag) {
+          selectedModelType.value = typeTag
+        }
+      }
+
+      currentStep.value = 2
+    } catch (error) {
+      console.error('Failed to retrieve metadata:', error)
+      uploadError.value =
+        error instanceof Error
+          ? error.message
+          : st(
+              'assetBrowser.uploadModelFailedToRetrieveMetadata',
+              'Failed to retrieve metadata. Please check the link and try again.'
+            )
+      currentStep.value = 1
+    } finally {
+      isFetchingMetadata.value = false
+    }
+  }
+
+  async function uploadModel() {
+    if (!canUploadModel.value) return
+
+    isUploading.value = true
+    uploadStatus.value = 'uploading'
+
+    try {
+      const tags = selectedModelType.value
+        ? ['models', selectedModelType.value]
+        : ['models']
+      const filename =
+        wizardData.value.metadata?.filename ||
+        wizardData.value.metadata?.name ||
+        'model'
+
+      await assetService.uploadAssetFromUrl({
+        url: wizardData.value.url,
+        name: filename,
+        tags,
+        user_metadata: {
+          source: 'civitai',
+          source_url: wizardData.value.url,
+          model_type: selectedModelType.value
+        }
+      })
+
+      uploadStatus.value = 'success'
+      currentStep.value = 3
+      return true
+    } catch (error) {
+      console.error('Failed to upload asset:', error)
+      uploadStatus.value = 'error'
+      uploadError.value =
+        error instanceof Error ? error.message : 'Failed to upload model'
+      currentStep.value = 3
+      return false
+    } finally {
+      isUploading.value = false
+    }
+  }
+
+  function goToPreviousStep() {
+    if (currentStep.value > 1) {
+      currentStep.value = currentStep.value - 1
+    }
+  }
+
+  return {
+    // State
+    currentStep,
+    isFetchingMetadata,
+    isUploading,
+    uploadStatus,
+    uploadError,
+    wizardData,
+    selectedModelType,
+
+    // Computed
+    canFetchMetadata,
+    canUploadModel,
+
+    // Actions
+    fetchMetadata,
+    uploadModel,
+    goToPreviousStep
+  }
+}