feat(ui): integrate failover controls into provider cards

- Add failover toggle button to provider card actions
- Show priority badge (P1, P2, ...) for queued providers
- Highlight active provider with green border in failover mode
- Sync drag-drop order with failover queue
- Move per-app failover toggle to FailoverQueueManager
- Simplify SettingsPage failover section

src/hooks/useProxyStatus.ts

@@ -75,6 +75,7 @@ export function useProxyStatus() {
       queryClient.invalidateQueries({ queryKey: ["proxyTakeoverStatus"] });
       // 清除所有供应商健康状态缓存（后端已清空数据库记录）
       queryClient.invalidateQueries({ queryKey: ["providerHealth"] });
+      // 注意：故障转移队列和开关状态会保留，不需要刷新
     },
     onError: (error: Error) => {
       const detail =