feat(download): add Hugging Face model download to standalone UI wizard (#965, #977)

Integrate HF model downloading into the existing CivitAI-style wizard flow:
- URL type detection (civitai / hf-resolve / hf-repo / direct-http)
- Repo file explorer with checkbox-based file selection
- Batch/queue download with per-file WebSocket progress
- Aria2 backend support (respects download_backend setting)
- Scanner cache integration via create_default_metadata + add_model_to_cache
- i18n updates for all 10 locales

static/js/api/baseModelApi.js

@@ -7,6 +7,7 @@ import {
     getCurrentModelType,
     isValidModelType,
     DOWNLOAD_ENDPOINTS,
+    HF_ENDPOINTS,
     WS_ENDPOINTS
 } from './apiConfig.js';
 import { resetAndReload } from './modelApiFactory.js';
@@ -1243,6 +1244,48 @@ export class BaseModelApiClient {
         }
     }
 
+    async fetchHfRepoFiles(repo, revision = 'main') {
+        try {
+            const params = new URLSearchParams({ repo, revision });
+            const response = await fetch(`${HF_ENDPOINTS.repoFiles}?${params}`);
+            if (!response.ok) {
+                const err = await response.json().catch(() => ({}));
+                throw new Error(err.error || 'Failed to fetch HF repo files');
+            }
+            return await response.json();
+        } catch (error) {
+            console.error('Error fetching HF repo files:', error);
+            throw error;
+        }
+    }
+
+    async downloadHfModel({ repo, filename, revision, modelRoot, relativePath, useDefaultPaths, download_id }) {
+        try {
+            const response = await fetch(HF_ENDPOINTS.download, {
+                method: 'POST',
+                headers: { 'Content-Type': 'application/json' },
+                body: JSON.stringify({
+                    repo,
+                    filename,
+                    revision: revision || 'main',
+                    model_root: modelRoot,
+                    relative_path: relativePath || '',
+                    use_default_paths: useDefaultPaths || false,
+                    ...(download_id ? { download_id } : {}),
+                })
+            });
+
+            if (!response.ok) {
+                throw new Error(await response.text());
+            }
+
+            return await response.json();
+        } catch (error) {
+            console.error('Error downloading HF model:', error);
+            throw error;
+        }
+    }
+
     _buildQueryParams(baseParams, pageState) {
         const params = new URLSearchParams(baseParams);
         const isExcludedView = pageState.viewMode === 'excluded';