fix: add backend dependency and retry logic to gateway bootstrap

Add depends_on backend service to gateway in docker-compose to ensure backend is available before gateway starts. Refactor gateway-entrypoint.sh to move bootstrap logic into apply_bundle function with error handling, enabling automatic retry on bootstrap failure instead of exiting immediately.

deploy/docker-compose.yml

@@ -55,6 +55,8 @@ services:
     build:
       context: .
       dockerfile: gateway/Dockerfile
+    depends_on:
+      - backend
     cap_add:
       - NET_ADMIN
       - SYS_MODULE