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

templates/components/modals/download_modal.html

@@ -14,7 +14,7 @@
                 <div class="error-message" id="urlError"></div>
                 <div class="input-hint">
                     <i class="fas fa-info-circle"></i>
-                    <span>{{ t('modals.download.urlHint') }}</span>
+                    <span id="urlHint">{{ t('modals.download.urlHint') }}</span>
                 </div>
             </div>
             <div class="modal-actions">
@@ -22,6 +22,24 @@
             </div>
         </div>
 
+        <!-- Step 1b: HF Repo File Explorer (shown when HF repo URL is detected) -->
+        <div class="download-step" id="repoFileStep" style="display: none;">
+            <div class="input-group">
+                <label>{{ t('modals.download.selectHfFiles') }}</label>
+                <div class="hf-repo-header">
+                    <span id="hfRepoLabel" class="hf-repo-label"></span>
+                </div>
+                <div class="repo-file-list" id="repoFileList">
+                    <!-- Files will be inserted here dynamically -->
+                </div>
+                <div class="error-message" id="repoFileError"></div>
+            </div>
+            <div class="modal-actions">
+                <button class="secondary-btn" id="backToUrlFromHfBtn">{{ t('common.actions.back') }}</button>
+                <button class="primary-btn" id="nextFromHfFiles">{{ t('common.actions.next') }}</button>
+            </div>
+        </div>
+
         <!-- Step 2: Batch Preview (multi-URL mode) -->
         <div class="download-step" id="batchPreviewStep" style="display: none;">
             <div class="batch-preview-list" id="batchPreviewList">