🚀 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.

controller/vendor_meta.go

@@ -65,6 +65,15 @@ func CreateVendorMeta(c *gin.Context) {
         common.ApiErrorMsg(c, "供应商名称不能为空")
         return
     }
+    // 创建前先检查名称
+    if dup, err := model.IsVendorNameDuplicated(0, v.Name); err != nil {
+        common.ApiError(c, err)
+        return
+    } else if dup {
+        common.ApiErrorMsg(c, "供应商名称已存在")
+        return
+    }
+
     if err := v.Insert(); err != nil {
         common.ApiError(c, err)
         return
@@ -83,10 +92,11 @@ func UpdateVendorMeta(c *gin.Context) {
         common.ApiErrorMsg(c, "缺少供应商 ID")
         return
     }
-    // 检查名称冲突
-    var dup int64
-    _ = model.DB.Model(&model.Vendor{}).Where("name = ? AND id <> ?", v.Name, v.Id).Count(&dup).Error
-    if dup > 0 {
+    // 名称冲突检查
+    if dup, err := model.IsVendorNameDuplicated(v.Id, v.Name); err != nil {
+        common.ApiError(c, err)
+        return
+    } else if dup {
         common.ApiErrorMsg(c, "供应商名称已存在")
         return
     }