fix: Add missing CONTAINER_2_NAME for Blue/Green deployment

Added CONTAINER_2_NAME environment variable to support proper Blue/Green
deployment. Without this, the GREEN variable was empty, causing containers
to be created with random names instead of team11_1/team11_2.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: JIWONKIMS

.github/workflows/deploy.yml

@@ -3,6 +3,7 @@ name: deploy.yml
 env:
   IMAGE_REPOSITORY: team11 # GHCR 이미지 리포지토리명(소유자 포함 X)
   CONTAINER_1_NAME: team11_1 # 슬롯1(고정 이름)
+  CONTAINER_2_NAME: team11_2 # 슬롯2(고정 이름)
   CONTAINER_PORT: 8080 # 컨테이너 내부 포트(스프링부트)
   EC2_INSTANCE_TAG_NAME: team11-terra-ec2-1 # 배포 대상 EC2 Name 태그
   DOCKER_NETWORK: common # 도커 네트워크