feat: 更新 Navbar 组件以添加 DownloadIcon，调整 AgentDetail 和 MonitorsList 页面布局样式

frontend/src/components/Navbar.tsx

@@ -22,7 +22,8 @@ import {
   CubeIcon,
   PieChartIcon,
   BellIcon,
-  HamburgerMenuIcon
+  HamburgerMenuIcon,
+  DownloadIcon
 } from "@radix-ui/react-icons";
 import { useAuth } from "../providers/AuthProvider";
 import { useState, useEffect } from "react";

frontend/src/pages/agents/AgentDetail.tsx

@@ -196,7 +196,7 @@ const AgentDetail = () => {
 
   return (
     <Container size="4">
-      <Flex justify="between" align="center">
+      <Flex justify="between" align="start" direction={{ initial: "column", sm: "row" }} gap="4">
         <Flex align="center" gap="2">
           <Button variant="secondary" onClick={() => navigate("/agents")}>
             <ArrowLeftIcon />
@@ -234,7 +234,7 @@ const AgentDetail = () => {
           </Button>
         </Flex>
       </Flex>
-      <Box pt="3">
+      <Box py="3">
         <Grid columns={{ initial: "1" }} gap="4">
           {/* 系统信息卡片 */}
           <Card>
@@ -380,7 +380,7 @@ const AgentDetail = () => {
           </Card>
 
           {/* Agent 资源信息卡片 */}
-          <Card>
+          <Card className="pr-4">
             <Flex direction="column" gap="2" className="ml-4">
               <Heading size="3">{t("agent.metrics")}</Heading>
               <AgentCard

frontend/src/pages/agents/AgentsList.tsx

@@ -350,7 +350,7 @@ const AgentsList = () => {
         </Flex>
       </Flex>
 
-      <Box className="mt-4 space-x-2">
+      <Box className="my-4 space-x-2">
         {agents.length === 0 ? (
           <Card>
             <Flex

frontend/src/pages/monitors/MonitorsList.tsx

@@ -231,7 +231,7 @@ const MonitorsList = () => {
         </Flex>
       </Flex>
 
-      <Container className="mt-4 space-x-2">
+      <Container className="my-4 space-x-2">
         {monitors.length === 0 ? (
           <Card>
             <Flex