fix: stop grouping HF/ModelScope models by repository

A repository is not a model identity: collection repos on Hugging Face
and ModelScope host many unrelated models, which were wrongly shown as
versions of each other.

- Hugging Face models no longer auto-group (the Hub exposes no
  site-native model id)
- ModelScope models group by the site's native published-model id
  (MuseInfo modelVersion.modelId), extracted during enrichment and
  persisted on the sidecar as source_model_id/source_version_id;
  unenriched models stay standalone instead of collapsing a whole repo
  into one group
- TensorArt grouping unchanged (its URL id is already model-level)
- Frontend group-key derivation mirrors the new backend semantics

static/js/components/shared/ModelCard.js

@@ -522,7 +522,7 @@ export function createModelCard(model, modelType) {
         card.dataset.modelId = modelId;
     } else {
         // For externally-sourced models, derive a group key from the source
-        // URL for version grouping (hf:user/repo, ms:user/repo, ta:<id>).
+        // identity for version grouping (ms:<model_id>, ta:<id>).
         const sourceGroupKey = getModelSourceGroupKey(model);
         if (sourceGroupKey) {
             card.dataset.modelId = sourceGroupKey;