feat(ui): show version count in group-by-model cards, add versions_count sort, no-reload VLM

- group_by_model dedup now counts versions per group and attaches
  version_count; respects update_flag_strategy (same_base) by
  sub-grouping on base_model
- Card footer shows clickable 'x versions' link instead of version
  name when grouped (hides HIGH/LOW badges); clicking triggers
  View Local Versions without page reload
- Added 'Local Versions' sort option (versions_count), auto-hidden
  when group_by_model is off
- Sort preference is saved/restored separately for normal and
  grouped modes
- VLM flow (triggerVlmView, clearCustomFilter) uses resetAndReload()
  via API instead of window.location.reload()
- Fixed cache mutation bug: version_count is now set on a shallow
  copy, not the cached dict, preventing stale version_count leaking
  into VLM responses
- i18n: all 9 locale files translated

static/css/style.css

@@ -59,3 +59,8 @@
 .initialization-notice .loading-spinner {
     margin-bottom: var(--space-2);
 }
+
+/* Hide versions_count sort option when group-by-model is off */
+body:not(.group-by-model) .sort-option-versions-count {
+    display: none;
+}