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/get-proto/index.d.ts

@@ -0,0 +1,5 @@
+declare function getProto<O extends object>(object: O): object | null;
+
+declare const x: typeof getProto | null;
+
+export = x;