🚀 refactor: migrate vendor-count aggregation to model layer & align frontend logic

Summary
• Backend
  – Moved duplicate-name validation and total vendor-count aggregation from controllers (`controller/model_meta.go`, `controller/vendor_meta.go`, `controller/prefill_group.go`) to model layer (`model/model_meta.go`, `model/vendor_meta.go`, `model/prefill_group.go`).
  – Added `GetVendorModelCounts()` and `Is*NameDuplicated()` helpers; controllers now call these instead of duplicating queries.
  – API response for `/api/models` now returns `vendor_counts` with per-vendor totals across all pages, plus `all` summary.
  – Removed redundant checks and unused imports, eliminating `go vet` warnings.

• Frontend
  – `useModelsData.js` updated to consume backend-supplied `vendor_counts`, calculate the `all` total once, and drop legacy client-side counting logic.
  – Simplified initial data flow: first render now triggers only one models request.
  – Deleted obsolete `updateVendorCounts` helper and related comments.
  – Ensured search flow also sets `vendorCounts`, keeping tab badges accurate.

Why
This refactor enforces single-responsibility (aggregation in model layer), delivers consistent totals irrespective of pagination, and removes redundant client queries, leading to cleaner code and better performance.

model/prefill_group.go

@@ -33,6 +33,16 @@ func (g *PrefillGroup) Insert() error {
     return DB.Create(g).Error
 }
 
+// IsPrefillGroupNameDuplicated 检查组名称是否重复（排除自身 ID）
+func IsPrefillGroupNameDuplicated(id int, name string) (bool, error) {
+    if name == "" {
+        return false, nil
+    }
+    var cnt int64
+    err := DB.Model(&PrefillGroup{}).Where("name = ? AND id <> ?", name, id).Count(&cnt).Error
+    return cnt > 0, err
+}
+
 // Update 更新组
 func (g *PrefillGroup) Update() error {
     g.UpdatedTime = common.GetTimestamp()