feat(mvp): phase 4 - app registry & healthcheck

Add app CRUD API endpoints, healthcheck service with node-cron scheduler,
icon resolver (Lucide, Simple Icons, CDN, uploads), app management UI
with Superforms, health badge component, and Docker health endpoint.

src/lib/server/jobs/healthcheckScheduler.ts

@@ -0,0 +1,39 @@
+import cron from 'node-cron';
+import { checkAllApps } from '$lib/server/services/healthcheckService.js';
+
+let scheduledTask: cron.ScheduledTask | null = null;
+
+/**
+ * Start the healthcheck scheduler.
+ * Runs checkAllApps on a cron schedule (default: every 60 seconds).
+ */
+export function startScheduler(cronExpression: string = '* * * * *'): void {
+	if (scheduledTask) {
+		return;
+	}
+
+	scheduledTask = cron.schedule(cronExpression, async () => {
+		try {
+			await checkAllApps();
+		} catch {
+			// Swallow errors to prevent scheduler crash
+		}
+	});
+
+	// Run an initial check shortly after startup
+	setTimeout(() => {
+		checkAllApps().catch(() => {
+			// Swallow initial check errors
+		});
+	}, 5000);
+}
+
+/**
+ * Stop the healthcheck scheduler.
+ */
+export function stopScheduler(): void {
+	if (scheduledTask) {
+		scheduledTask.stop();
+		scheduledTask = null;
+	}
+}