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/es-define-property/tsconfig.json

@@ -0,0 +1,10 @@
+{
+	"extends": "@ljharb/tsconfig",
+	"compilerOptions": {
+		"target": "es2022",
+	},
+	"exclude": [
+		"coverage",
+		"test/list-exports"
+	],
+}