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/call-bind-apply-helpers/actualApply.js

@@ -0,0 +1,10 @@
+'use strict';
+
+var bind = require('function-bind');
+
+var $apply = require('./functionApply');
+var $call = require('./functionCall');
+var $reflectApply = require('./reflectApply');
+
+/** @type {import('./actualApply')} */
+module.exports = $reflectApply || bind.call($call, $apply);