fix: polish split-port implementation for merge

- Add 30s timeout to API bridge proxy requests to prevent resource exhaustion
- Extract healthcheck.mjs script (replaces inline node -e in Dockerfile + compose files)
- Add unit tests for runtime port resolution (14 tests, parsePort + resolveRuntimePorts)
- Fix formatting in declare global block

scripts/healthcheck.mjs

@@ -0,0 +1,14 @@
+#!/usr/bin/env node
+
+/**
+ * Docker healthcheck script for OmniRoute.
+ * Checks the /api/settings endpoint on the dashboard port.
+ * Used by Dockerfile and docker-compose files.
+ */
+const port = process.env.DASHBOARD_PORT || process.env.PORT || "20128";
+
+fetch(`http://127.0.0.1:${port}/api/settings`)
+  .then((r) => {
+    if (!r.ok) throw new Error(`HTTP ${r.status}`);
+  })
+  .catch(() => process.exit(1));