feat(mcp): add import button to import MCP servers from apps

- Add import_mcp_from_apps command that reuses existing import logic
- Add Import button in MCP panel header (consistent with Skills)
- Fix import count to only return truly new servers (not already in DB)
- Update translations for import success/no-import messages (zh/en/ja)

src/hooks/useMcp.ts

@@ -59,3 +59,16 @@ export function useDeleteMcpServer() {
     },
   });
 }
+
+/**
+ * 从所有应用导入 MCP 服务器
+ */
+export function useImportMcpFromApps() {
+  const queryClient = useQueryClient();
+  return useMutation({
+    mutationFn: () => mcpApi.importFromApps(),
+    onSuccess: () => {
+      queryClient.invalidateQueries({ queryKey: ["mcp", "all"] });
+    },
+  });
+}