refactor: 重构上游模型获取与展示逻辑

- 后端支持遍历所有活跃 API Key 聚合模型，按 model id 合并 api_formats
- 前端移除按 API 格式分组，改为统一展示并内联显示格式标签
- 改进 401 错误处理，账户异常时清除认证并重定向首页

frontend/src/features/providers/components/ModelMappingDialog.vue

@@ -264,7 +264,8 @@ import {
 import { useToast } from '@/composables/useToast'
 import {
   type Model,
-  type ProviderModelAlias
+  type ProviderModelAlias,
+  type UpstreamModel,
 } from '@/api/endpoints'
 import { updateModel } from '@/api/endpoints/models'
 import { useUpstreamModelsCache } from '../composables/useUpstreamModelsCache'
@@ -311,7 +312,7 @@ const searchQuery = ref('')
 const collapsedGroups = ref<Set<string>>(new Set())
 
 // 上游模型
-const upstreamModels = ref<{ id: string; api_format?: string }[]>([])
+const upstreamModels = ref<UpstreamModel[]>([])
 
 // 表单数据
 const formData = ref<{