feat: 自动备份与保留策略、健康持续化与状态页、指标历史与趋势图，并修隧道判定误报与仪表盘布局（v1.2.11）

- 自动备份：每日一份（按最新备份是否在 24h 内判定，重启不重复）、保留份数可配、列表/下载/恢复/删除，恢复前先校验归档；顺手修 writeArchive 逐个检查 tar/gzip/文件 Close()（审查报告 §二）

- 健康持续化：只存状态变更（up/down/unknown）并推导可用率与不可用区间；公开状态页默认关闭、访问码存 SHA-256、按 IP 限流、只暴露域名与可用率

- 隧道判定修复：RouteHealthCandidate 新增 tunnel_known，frps 管理接口不可用时不再把「判不出来」当成「不通」（此前会误报「隧道连续不通」）；汇总与徽标同样区分「无法判定」

- 指标历史：metrics_samples 纵向点表（本机 CPU/内存/磁盘 + 每规则上下行，30 天保留、查询按桶平均、不做降采样表）；仪表盘趋势卡支持 1h/24h/7d

- 仪表盘布局：运行状态并入顶部统计区（运行时长补进「服务」卡）；性能并入系统资源那一行，整行 4 列

- 测试：backup/metrics/frp/api/app 新增用例；gofmt、go build/vet/test、vue-tsc、vite build 全绿

- agent 无改动，AgentVersion 保持 0.12.2

internal/notify/store.go

@@ -99,6 +99,8 @@ func (s *Store) load(ctx context.Context, decrypt bool) (Config, runtimeSecrets,
 		cfg.OnFrpsDown = flag(s.settings, ctx, settings.KeyNotifyOnFrpsDown, false)
 		cfg.OnAgentUnreachable = flag(s.settings, ctx, settings.KeyNotifyOnAgentUnreachable, false)
 		cfg.OnRouteDrift = flag(s.settings, ctx, settings.KeyNotifyOnRouteDrift, false)
+		// 备份失败属于「你以为有备份其实没有」，默认开启
+		cfg.OnBackupFailure = flag(s.settings, ctx, settings.KeyNotifyOnBackupFailure, true)
 	} else {
 		legacyDDNS := flag(s.settings, ctx, settings.KeyNotifyOnDDNSError, true)
 		legacyCert := flag(s.settings, ctx, settings.KeyNotifyOnCertError, true)
@@ -202,6 +204,7 @@ func hasNotifyEventSettings(ctx context.Context, store *settings.Store) bool {
 		settings.KeyNotifyOnFrpsDown,
 		settings.KeyNotifyOnAgentUnreachable,
 		settings.KeyNotifyOnRouteDrift,
+		settings.KeyNotifyOnBackupFailure,
 	}
 	for _, key := range keys {
 		raw, err := store.Get(ctx, key)
@@ -271,6 +274,9 @@ func (s *Store) Save(ctx context.Context, in SaveInput) error {
 	if err := s.settings.SetBool(ctx, settings.KeyNotifyOnRouteDrift, in.OnRouteDrift); err != nil {
 		return err
 	}
+	if err := s.settings.SetBool(ctx, settings.KeyNotifyOnBackupFailure, in.OnBackupFailure); err != nil {
+		return err
+	}
 	if err := s.settings.SetInt(ctx, settings.KeyNotifyFrpsFailThreshold, clampThreshold(in.FrpsFailThreshold, DefaultFrpsFailThreshold)); err != nil {
 		return err
 	}
@@ -523,6 +529,7 @@ func ParseSaveInputFromMap(values map[string]string) (SaveInput, bool) {
 	in.OnFrpsDown = values[settings.KeyNotifyOnFrpsDown] == "1" || strings.EqualFold(values[settings.KeyNotifyOnFrpsDown], "true")
 	in.OnAgentUnreachable = values[settings.KeyNotifyOnAgentUnreachable] == "1" || strings.EqualFold(values[settings.KeyNotifyOnAgentUnreachable], "true")
 	in.OnRouteDrift = values[settings.KeyNotifyOnRouteDrift] == "1" || strings.EqualFold(values[settings.KeyNotifyOnRouteDrift], "true")
+	in.OnBackupFailure = values[settings.KeyNotifyOnBackupFailure] == "1" || strings.EqualFold(values[settings.KeyNotifyOnBackupFailure], "true")
 	in.FrpsFailThreshold = intSettingFromMap(values, settings.KeyNotifyFrpsFailThreshold, DefaultFrpsFailThreshold)
 	in.AgentFailThreshold = intSettingFromMap(values, settings.KeyNotifyAgentFailThreshold, DefaultAgentFailThreshold)
 	in.DriftCooldownHours = intSettingFromMap(values, settings.KeyNotifyDriftCooldownHours, DefaultDriftCooldownHours)