💰 feat: Add model billing type (quota_type) support across backend & frontend

Summary
• Backend
  1. model/model_meta.go
     – Added `QuotaType` field to `Model` struct (JSON only, gorm `-`).
  2. model/model_groups.go
     – Implemented `GetModelQuotaType(modelName)` leveraging cached pricing map.
  3. controller/model_meta.go
     – Enhanced `fillModelExtra` to populate `QuotaType` using new helper.

• Frontend
  1. web/src/components/table/models/ModelsColumnDefs.js
     – Introduced `renderQuotaType` helper that visualises billing mode with coloured tags (`teal = per-call`, `violet = per-token`).
     – Added “计费类型” column (`quota_type`) to models table.

Why
Providing the billing mode alongside existing pricing/group information gives administrators instant visibility into whether each model is priced per call or per token, aligning UI with new backend metadata.

Notes
No database migration required – `quota_type` is transient, delivered via API. Frontend labels/colours can be adjusted via i18n or theme tokens if necessary.

web/src/components/table/models/ModelsColumnDefs.js

@@ -98,6 +98,25 @@ const renderEndpoints = (text) => {
   });
 };
 
+// Render quota type
+const renderQuotaType = (qt, t) => {
+  if (qt === 1) {
+    return (
+      <Tag color='teal' size='small' shape='circle'>
+        {t('按次计费')}
+      </Tag>
+    );
+  }
+  if (qt === 0) {
+    return (
+      <Tag color='violet' size='small' shape='circle'>
+        {t('按量计费')}
+      </Tag>
+    );
+  }
+  return qt ?? '-';
+};
+
 // Render bound channels
 const renderBoundChannels = (channels) => {
   if (!channels || channels.length === 0) return '-';
@@ -213,6 +232,11 @@ export const getModelsColumns = ({
       dataIndex: 'enable_groups',
       render: renderGroups,
     },
+    {
+      title: t('计费类型'),
+      dataIndex: 'quota_type',
+      render: (qt) => renderQuotaType(qt, t),
+    },
     {
       title: t('创建时间'),
       dataIndex: 'created_time',