feat(health-check): introduce health probe gap configuration and enhance health check logic

Added `healthProbeGapMs` configuration to control the minimum pause between probes to different physical targets. Updated health check service to utilize this configuration, ensuring efficient probing without overwhelming the targets. Enhanced the `runAllChecks` function to group probes by physical IP and implement the new gap logic. Updated related tests to validate the new functionality.

apps/api/src/config.ts

@@ -14,6 +14,8 @@ export interface AppConfig {
   healthDegradedFailures: number;
   healthDownFailures: number;
   healthLatencyWarnMs: number;
+  /** Min pause between probes to different physical targets (same IP is probed once). */
+  healthProbeGapMs: number;
   logLevel: string;
   /** Portal SSO — when true, require portal JWT with apps includes cfdm */
   authRequired: boolean;
@@ -46,12 +48,14 @@ export function loadConfig(): AppConfig {
       ? resolve(process.env.STATIC_DIR)
       : null,
     certCheckCron: process.env.CERT_CHECK_CRON ?? "0 0 */6 * * *",
-    healthCheckCron: process.env.HEALTH_CHECK_CRON ?? "*/30 * * * * *",
+    // Default: every 2 minutes (was every 30s — hammered origins / anti-bot).
+    healthCheckCron: process.env.HEALTH_CHECK_CRON ?? "0 */2 * * * *",
     healthDegradedFailures:
       Number(process.env.HEALTH_DEGRADED_FAILURES ?? "1") || 1,
     healthDownFailures: Number(process.env.HEALTH_DOWN_FAILURES ?? "2") || 2,
     healthLatencyWarnMs:
       Number(process.env.HEALTH_LATENCY_WARN_MS ?? "1000") || 1000,
+    healthProbeGapMs: Number(process.env.HEALTH_PROBE_GAP_MS ?? "2000") || 2000,
     logLevel: process.env.LOG_LEVEL ?? "info",
     authRequired: boolEnv(process.env.AUTH_REQUIRED, false),
     authIssuer: