feat(vlm): sort versions by newest first in VLM view, with disabled sort dropdown

When viewing all versions of a model (VLM mode via 'x versions' button):
- Backend always sorts by version ID descending, ignoring current sort_by
- A temporary 'Newest version first' option is injected into the sort
  dropdown (removed on exit, not a permanent option)
- The sort dropdown is disabled (greyed out) while VLM is active
- On clearing VLM, the previous sort preference is restored and the
  dropdown re-enabled
- Handles stale VLM state (e.g. after page reload with leftover session)
- Covers all three model page types: loras, checkpoints, embeddings

Also fixes review nits:
- Correct i18n call pattern (defaultValue in options object)
- Shared _restoreSortAfterVlm() helper to avoid triple duplication

static/css/layout.css

@@ -264,6 +264,23 @@
     box-shadow: 0 0 0 2px oklch(var(--lora-accent) / 0.15);
 }
 
+/* Disabled sort dropdown — used when VLM custom filter is active */
+.control-group select:disabled {
+    opacity: 0.5;
+    cursor: not-allowed;
+    background-color: var(--bg-color);
+    border-color: var(--border-color);
+    box-shadow: none;
+    transform: none;
+}
+
+.control-group select:disabled:hover {
+    border-color: var(--border-color);
+    background-color: var(--bg-color);
+    transform: none;
+    box-shadow: none;
+}
+
 /* Ensure hidden class works properly */
 .hidden {
     display: none !important;