feat: Agent采集uptime, 后端持久化kernel/uptime/diskIO, 前端磁盘BPS+IOPS展示

- Agent: system.go 添加 readUptime(), SystemStat 携带 Uptime
- Backend: Server 模型新增 Kernel 字段, ReceiveReport 持久化 kernel+uptime
- Backend: /agent/latest 返回 kernel/uptime/port_info/disk_io_info/disk_total
- Frontend: 磁盘监控改为 BPS+IOPS (4张卡片), 系统信息修复内核/运行时长/监听端口/磁盘容量
- 图表单位从 MB/s 改为 KB/s, 添加 formatBPS 工具函数

backend/internal/models/navigation.go

@@ -3,7 +3,6 @@ package models
 import (
 	"time"
 
-	"gorm.io/gorm"
 )
 
 // NavigationGroup 导航分组模型
@@ -18,12 +17,11 @@ type NavigationGroup struct {
 	LinkCount   int            `gorm:"default:0" json:"link_count"`
 	CreatedAt   time.Time      `json:"created_at"`
 	UpdatedAt   time.Time      `json:"updated_at"`
-	DeletedAt   gorm.DeletedAt `gorm:"index" json:"-"`
 }
 
 // TableName 表名
 func (NavigationGroup) TableName() string {
-	return "navigation_groups"
+	return "sys_navigation_groups"
 }
 
 // NavigationLink 导航链接模型
@@ -40,7 +38,6 @@ type NavigationLink struct {
 	Enabled     bool           `gorm:"default:true" json:"enabled"`
 	CreatedAt   time.Time      `json:"created_at"`
 	UpdatedAt   time.Time      `json:"updated_at"`
-	DeletedAt   gorm.DeletedAt `gorm:"index" json:"-"`
 
 	// 关联
 	Group *NavigationGroup `json:"group,omitempty"`