🚀 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.

web/src/components/table/models/ModelsActions.jsx

@@ -23,6 +23,7 @@ import PrefillGroupManagement from './modals/PrefillGroupManagement.jsx';
 import { Button, Space, Modal } from '@douyinfe/semi-ui';
 import CompactModeToggle from '../../common/ui/CompactModeToggle';
 import { showError } from '../../../helpers';
+import SelectionNotification from './components/SelectionNotification.jsx';
 
 const ModelsActions = ({
   selectedKeys,
@@ -70,14 +71,6 @@ const ModelsActions = ({
           {t('添加模型')}
         </Button>
 
-        <Button
-          type='danger'
-          className="flex-1 md:flex-initial"
-          onClick={handleDeleteSelectedModels}
-          size="small"
-        >
-          {t('删除所选模型')}
-        </Button>
 
         <Button
           type="secondary"
@@ -104,6 +97,12 @@ const ModelsActions = ({
         />
       </div>
 
+      <SelectionNotification
+        selectedKeys={selectedKeys}
+        t={t}
+        onDelete={handleDeleteSelectedModels}
+      />
+
       <Modal
         title={t('批量删除模型')}
         visible={showDeleteModal}