fix(ui): unify HF file selection UI, remove cloud icon, add select-all, cleanup dead code (#965, #977)

- Unify single-URL and multi-URL HF repo flows to use the same batch
  preview interface (remove separate repoFileStep)
- Remove unnecessary cloud icon from HF batch preview items
- Use formatFileSize() instead of hardcoded MB text
- Change default selection to unchecked (no preselected files)
- Add select all / deselect all checkbox with dynamic Next button
- Clean up dead CSS, HTML template, and JS methods from removed
  repoFileStep
- Add selectAll i18n key with translations for all 10 locales
- Fix batch progress bar name fallback for HF items

static/css/components/modal/download-modal.css

@@ -823,87 +823,6 @@
     background: var(--lora-surface);
 }
 
-/* HF Repo File Explorer Step */
-.hf-repo-header {
-    margin-bottom: var(--space-2);
-    font-size: 0.95em;
-    color: var(--text-color);
-    opacity: 0.8;
-}
-
-.repo-file-list {
-    max-height: 360px;
-    overflow-y: auto;
-    margin: var(--space-2) 0;
-    display: flex;
-    flex-direction: column;
-    gap: 6px;
-}
-
-.repo-file-item {
-    display: flex;
-    align-items: center;
-    gap: 10px;
-    padding: 10px 12px;
-    border: 1px solid var(--border-color);
-    border-radius: var(--border-radius-sm);
-    cursor: pointer;
-    transition: var(--transition-base);
-    background: var(--bg-color);
-}
-
-.repo-file-item:hover {
-    border-color: var(--lora-accent);
-    box-shadow: var(--shadow-sm);
-}
-
-.repo-file-item.selected {
-    border: 2px solid var(--lora-accent);
-    background: oklch(var(--lora-accent) / 0.05);
-}
-
-.repo-file-item .repo-file-checkbox {
-    width: 18px;
-    height: 18px;
-    cursor: pointer;
-    accent-color: var(--lora-accent);
-    flex-shrink: 0;
-    padding: 0;
-    border: none;
-}
-
-.repo-file-icon {
-    font-size: 1.2em;
-    color: var(--text-color);
-    opacity: 0.6;
-    width: 24px;
-    text-align: center;
-    flex-shrink: 0;
-}
-
-.repo-file-name {
-    flex: 1;
-    font-weight: 500;
-    font-size: 0.95em;
-    word-break: keep-all;
-    overflow-wrap: anywhere;
-    min-width: 0;
-}
-
-.repo-file-meta {
-    display: flex;
-    align-items: center;
-    gap: 8px;
-    font-size: 0.85em;
-    color: var(--text-color);
-    opacity: 0.6;
-    white-space: nowrap;
-}
-
-.repo-file-size {
-    font-variant-numeric: tabular-nums;
-}
-
 .hf-badge {
     display: inline-block;
     padding: 1px 6px;
@@ -915,9 +834,6 @@
     margin-left: 4px;
 }
 
-[data-theme="dark"] .repo-file-item {
-    background: var(--lora-surface);
-}
 
 /* Checkbox inside HF batch preview items */
 .batch-preview-checkbox {
@@ -929,4 +845,42 @@
     padding: 0;
     border: none;
     margin: 0;
-}
+}
+
+/* Select All toolbar in batch preview */
+.batch-preview-select-all {
+    display: flex;
+    align-items: center;
+    gap: 8px;
+    padding: 8px 12px;
+    border-bottom: 1px solid var(--border-color);
+    background: var(--lora-surface);
+    cursor: pointer;
+    position: sticky;
+    top: 0;
+    z-index: 1;
+}
+
+.batch-preview-select-all input[type="checkbox"] {
+    width: 18px;
+    height: 18px;
+    cursor: pointer;
+    accent-color: var(--lora-accent);
+    flex-shrink: 0;
+    padding: 0;
+    border: none;
+    margin: 0;
+}
+
+.batch-preview-select-all label {
+    cursor: pointer;
+    font-size: 0.9em;
+    color: var(--text-color);
+    font-weight: 500;
+    margin: 0;
+    user-select: none;
+}
+
+[data-theme="dark"] .batch-preview-select-all {
+    background: var(--lora-surface);
+}