feat(API-11): Route API calls through AgilitonAPI gateway

Add gateway-first pattern: when AGILITON_API_KEY is set, route all
external API calls through the gateway with X-API-Key auth. Falls back
to direct API access when gateway is unavailable.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

node_modules/zod/v3/errors.js

@@ -0,0 +1,9 @@
+import defaultErrorMap from "./locales/en.js";
+let overrideErrorMap = defaultErrorMap;
+export { defaultErrorMap };
+export function setErrorMap(map) {
+    overrideErrorMap = map;
+}
+export function getErrorMap() {
+    return overrideErrorMap;
+}