feat: 重构监控中心导航，新增资源监控4大模块

- 主菜单「监控告警」→「监控中心」
- 「告警中心」→「告警服务」移至链路追踪下方
- 新增资源监控 Tab 页（主机/中间件/SNMP/站点拨测）
- Agent 新增网络采集器(network)和磁盘IO采集器(diskio)
- 后端扩展 Agent 上报模型，支持 NetworkStat/DiskIOStat
- 前端 ServerTableRow 展示网络和磁盘IO实时指标
- WebSocket MetricsUpdate 推送扩展

agent/collector/diskio.go

@@ -0,0 +1,121 @@
+// Package collector — 磁盘 IO 指标采集器
+// 通过读取 /proc/diskstats 获取磁盘读写 BPS 和 IOPS。
+//
+// 署名 Hermes
+package collector
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"strconv"
+	"strings"
+	"sync"
+	"time"
+
+	"ezops/agent/model"
+)
+
+// diskIOSample 保存上一次采样，用于计算速率
+type diskIOSample struct {
+	time       time.Time
+	readSects  uint64
+	writeSects uint64
+	readOps    uint64
+	writeOps   uint64
+}
+
+// DiskIOCollector 磁盘 IO 采集器
+type DiskIOCollector struct {
+	mu   sync.Mutex
+	prev *diskIOSample
+}
+
+// NewDiskIOCollector 创建磁盘 IO 采集器
+func NewDiskIOCollector() *DiskIOCollector {
+	return &DiskIOCollector{}
+}
+
+// Collect 采集磁盘 IO 指标
+func (c *DiskIOCollector) Collect() (model.DiskIOStat, error) {
+	stat := model.DiskIOStat{}
+
+	rSects, wSects, rOps, wOps, err := readDiskStats()
+	if err != nil {
+		return stat, fmt.Errorf("读取磁盘 IO 失败: %w", err)
+	}
+
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	now := time.Now()
+	cur := &diskIOSample{
+		time:       now,
+		readSects:  rSects,
+		writeSects: wSects,
+		readOps:    rOps,
+		writeOps:   wOps,
+	}
+
+	if c.prev != nil && now.After(c.prev.time) {
+		elapsed := now.Sub(c.prev.time).Seconds()
+		if elapsed > 0 {
+			sectorSize := uint64(512) // 标准扇区 512 bytes
+			stat.ReadBPS = float64((cur.readSects-c.prev.readSects)*sectorSize) / elapsed
+			stat.WriteBPS = float64((cur.writeSects-c.prev.writeSects)*sectorSize) / elapsed
+			stat.ReadIOPS = float64(cur.readOps-c.prev.readOps) / elapsed
+			stat.WriteIOPS = float64(cur.writeOps-c.prev.writeOps) / elapsed
+		}
+	}
+	c.prev = cur
+
+	return stat, nil
+}
+
+// readDiskStats 读取 /proc/diskstats，汇总所有物理磁盘的读写数据
+// fields[2]=设备名, fields[3]=读完成次数, fields[5]=读扇区数, fields[7]=写完成次数, fields[9]=写扇区数
+func readDiskStats() (rSects, wSects, rOps, wOps uint64, err error) {
+	f, err := os.Open("/proc/diskstats")
+	if err != nil {
+		return 0, 0, 0, 0, err
+	}
+	defer f.Close()
+
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		line := scanner.Text()
+		fields := strings.Fields(line)
+		if len(fields) < 14 {
+			continue
+		}
+
+		dev := fields[2]
+		// 只采集物理磁盘 (sdX, nvmeXn1, vdX)，跳过分区和 loop 设备
+		if strings.HasPrefix(dev, "loop") ||
+			(strings.HasPrefix(dev, "sd") && len(dev) > 3) || // sda1, sda2 等分区
+			(strings.HasPrefix(dev, "nvme") && strings.Contains(dev, "p")) || // nvme0n1p1
+			(strings.HasPrefix(dev, "ram")) ||
+			strings.HasPrefix(dev, "dm-") {
+			continue
+		}
+
+		// field 3 = 读完成次数 (rd_ios)
+		// field 5 = 读扇区数 (rd_sectors)
+		// field 7 = 写完成次数 (wr_ios)
+		// field 9 = 写扇区数 (wr_sectors)
+		if v, e := strconv.ParseUint(fields[3], 10, 64); e == nil {
+			rOps += v
+		}
+		if v, e := strconv.ParseUint(fields[5], 10, 64); e == nil {
+			rSects += v
+		}
+		if v, e := strconv.ParseUint(fields[7], 10, 64); e == nil {
+			wOps += v
+		}
+		if v, e := strconv.ParseUint(fields[9], 10, 64); e == nil {
+			wSects += v
+		}
+	}
+
+	return rSects, wSects, rOps, wOps, scanner.Err()
+}