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/dotenv/config.js

@@ -0,0 +1,9 @@
+(function () {
+  require('./lib/main').config(
+    Object.assign(
+      {},
+      require('./lib/env-options'),
+      require('./lib/cli-options')(process.argv)
+    )
+  )
+})()