fix(railway): use Dockerfile builder and remove invalid startCommand

- Changed from NIXPACKS to DOCKERFILE builder
- Removed startCommand (Dockerfile has CMD)
- Fixes: 'Build failed to leave the wheelhouse' error

railway.toml

@@ -1,8 +1,7 @@
 [build]
-builder = "NIXPACKS"
+builder = "DOCKERFILE"
 
 [deploy]
-startCommand = "node main.js"
 healthcheckPath = "/api/v1/health"
 healthcheckTimeout = 300
 restartPolicyType = "ON_FAILURE"