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/tsx/dist/repl.mjs

@@ -0,0 +1,3 @@
+var m=Object.defineProperty;var t=(o,r)=>m(o,"name",{value:r,configurable:!0});import p from"node:repl";import{v as l}from"./package-CeBgXWuR.mjs";import{t as c}from"./index-7AaEi15b.mjs";import"node:url";import"esbuild";import"node:crypto";import"node:fs";import"node:path";import"node:os";import"./temporary-directory-CwHp0_NW.mjs";console.log(`Welcome to tsx v${l} (Node.js ${process.version}).
+Type ".help" for more information.`);const s=p.start(),{eval:f}=s,v=t(async function(o,r,e,i){const n=await c(o,e,{loader:"ts",tsconfigRaw:{compilerOptions:{preserveValueImports:!0}},define:{require:"global.require"}}).catch(a=>(console.log(a.message),{code:`
+`}));return f.call(this,n.code,r,e,i)},"preEval");s.eval=v;