fix(mcp): surface per-app failures when importing MCP servers from apps

import_mcp_from_apps swallowed every importer error with unwrap_or(0),
so a corrupt config.toml surfaced as "imported 0 servers" with no hint
that anything went wrong.

Move the aggregation into McpService::import_from_all_apps: each app
imports best-effort (one bad file doesn't block the rest), and failures
are collected into a single error naming the failing apps alongside the
count that did import. The frontend now refreshes the server list on
settle rather than success, since a partial failure still means new
servers were persisted.

src/hooks/useMcp.ts

@@ -67,7 +67,9 @@ export function useImportMcpFromApps() {
   const queryClient = useQueryClient();
   return useMutation({
     mutationFn: () => mcpApi.importFromApps(),
-    onSuccess: () => {
+    // 后端是 best-effort 导入：部分应用失败会返回错误，但其余应用的
+    // 服务器已经入库，失败时也要刷新列表。
+    onSettled: () => {
       queryClient.invalidateQueries({ queryKey: ["mcp", "all"] });
     },
   });