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/hasown/index.js

@@ -0,0 +1,8 @@
+'use strict';
+
+var call = Function.prototype.call;
+var $hasOwn = Object.prototype.hasOwnProperty;
+var bind = require('function-bind');
+
+/** @type {import('.')} */
+module.exports = bind.call(call, $hasOwn);