Add outbound heartbeat monitoring (#1729)

* feat: add outbound heartbeat monitoring to external endpoints

Allow Beszel hub to periodically ping an external monitoring service
(e.g. BetterStack, Uptime Kuma, Healthchecks.io) with system status
summaries, enabling monitoring without exposing Beszel to the internet.

Configuration via environment variables:
- BESZEL_HUB_HEARTBEAT_URL: endpoint to ping (required to enable)
- BESZEL_HUB_HEARTBEAT_INTERVAL: seconds between pings (default: 60)
- BESZEL_HUB_HEARTBEAT_METHOD: HTTP method - POST/GET/HEAD (default: POST)

internal/site/src/components/routes/settings/layout.tsx

@@ -2,7 +2,14 @@ import { t } from "@lingui/core/macro"
 import { Trans, useLingui } from "@lingui/react/macro"
 import { useStore } from "@nanostores/react"
 import { getPagePath, redirectPage } from "@nanostores/router"
-import { AlertOctagonIcon, BellIcon, FileSlidersIcon, FingerprintIcon, SettingsIcon } from "lucide-react"
+import {
+	AlertOctagonIcon,
+	BellIcon,
+	FileSlidersIcon,
+	FingerprintIcon,
+	HeartPulseIcon,
+	SettingsIcon,
+} from "lucide-react"
 import { lazy, useEffect } from "react"
 import { $router } from "@/components/router.tsx"
 import { Card, CardContent, CardDescription, CardHeader, CardTitle } from "@/components/ui/card.tsx"
@@ -18,12 +25,14 @@ const notificationsSettingsImport = () => import("./notifications.tsx")
 const configYamlSettingsImport = () => import("./config-yaml.tsx")
 const fingerprintsSettingsImport = () => import("./tokens-fingerprints.tsx")
 const alertsHistoryDataTableSettingsImport = () => import("./alerts-history-data-table.tsx")
+const heartbeatSettingsImport = () => import("./heartbeat.tsx")
 
 const GeneralSettings = lazy(generalSettingsImport)
 const NotificationsSettings = lazy(notificationsSettingsImport)
 const ConfigYamlSettings = lazy(configYamlSettingsImport)
 const FingerprintsSettings = lazy(fingerprintsSettingsImport)
 const AlertsHistoryDataTableSettings = lazy(alertsHistoryDataTableSettingsImport)
+const HeartbeatSettings = lazy(heartbeatSettingsImport)
 
 export async function saveSettings(newSettings: Partial<UserSettings>) {
 	try {
@@ -88,6 +97,13 @@ export default function SettingsLayout() {
 			admin: true,
 			preload: configYamlSettingsImport,
 		},
+		{
+			title: t`Heartbeat`,
+			href: getPagePath($router, "settings", { name: "heartbeat" }),
+			icon: HeartPulseIcon,
+			admin: true,
+			preload: heartbeatSettingsImport,
+		},
 	]
 
 	const page = useStore($router)
@@ -141,5 +157,7 @@ function SettingsContent({ name }: { name: string }) {
 			return <FingerprintsSettings />
 		case "alert-history":
 			return <AlertsHistoryDataTableSettings />
+		case "heartbeat":
+			return <HeartbeatSettings />
 	}
 }