RHL-005-feat(env): add environment variable validation script

scripts/validate-env.mjs

@@ -0,0 +1,11 @@
+// scripts/validate-env.mjs
+import { validateEnv } from "../lib/config/validateEnv.js";
+
+try {
+	validateEnv(process.env);
+	// Keep output minimal, but explicit:
+	console.log("✅ Environment variables: OK");
+} catch (err) {
+	console.error(String(err?.message || err));
+	process.exit(1);
+}