feat: expose metrics from Victoria

[gsanchietti]

Since netdata will be removed, switch monitor to Victoria Metrics by including a new page inside Monitoring section.

See companion PR: NethServer/nethsecurity#1633

Example:

[Copilot]

Pull request overview

This PR updates the Monitoring area to support the post-netdata monitoring stack by adding a new Metrics page that fetches historical data from Telegraf/VictoriaMetrics, and by repointing existing ping-latency configuration calls away from Netdata.

Changes:

• Switch Ping Latency Monitor configuration UBUS service from ns.netdata to ns.telegraf.
• Add a new Monitoring → Metrics page (route + side menu entry) with time-range and auto-refresh controls.
• Introduce a metrics chart composable and UI components to render System and Network metric charts.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
src/views/standalone/monitoring/PingLatencyMonitorView.vue	Repoints configuration calls from Netdata to Telegraf.
src/views/standalone/monitoring/MetricsView.vue	New metrics page: controls + query to fetch historical metrics.
src/router/index.ts	Adds route for the new metrics page.
src/i18n/en.json	Adds English strings for the new Metrics UI.
src/composables/useMetricsCharts.ts	New composable to transform metrics payload into chart-ready data/options.
src/components/standalone/SideMenu.vue	Adds “Metrics” entry under Monitoring.
src/components/standalone/monitoring/metrics/SystemMetricsSection.vue	New “System” charts section layout.
src/components/standalone/monitoring/metrics/NetworkMetricsSection.vue	New “Network” charts section layout (traffic/packets/connections/latency/quality).
src/components/standalone/monitoring/metrics/MetricChartCard.vue	Shared card component rendering a TimeLineChart or an empty state.

Comments suppressed due to low confidence (1)

src/views/standalone/monitoring/PingLatencyMonitorView.vue:54

• The backend was switched to ns.telegraf, but the error title still uses the error.cannot_retrieve_netdata_configuration i18n key (see the catch block below). In some locales this message explicitly mentions Netdata, which is now misleading. Please introduce a Telegraf/Victoria-specific (or generic) key and use it here.

    const res = await ubusCall('ns.telegraf', 'get-configuration', {})
    if (res?.data?.hosts) {
      formPing.value.hostList = res.data.hosts
    }
  } catch (exception: any) {

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[gsanchietti]

Addressed the review feedback from this round:

• Metrics preferences now use the existing per-user preference helpers and the stored values are validated before use.
• Time-range labels were reduced to parameterized i18n entries.
• TimeLineChart now lets custom options override defaults.
• The empty-state icon now uses faChartLine.
• The Telegraf configuration error uses a dedicated translation key.

All review threads from this pass are resolved.