feat(deploy): implement blue-green deployment strategy

This commit replaces the previous deployment mechanism with a blue-green strategy to lay the groundwork for zero-downtime deployments.
Key changes:
Introduces a deploy-blue-green.sh script to manage "blue" and "green" container sets, creating versioned releases.
Updates the Anubis gatekeeper template to dynamically route traffic based on the active deployment color, allowing for seamless traffic switching.
Modifies Docker Compose files to include color-specific labels and environment variables.
Adapts the GitHub Actions workflow to execute the new blue-green deployment process.
Removes the old, now-obsolete deployment and health check scripts.
Note: Automated rollback on health check failure is not yet implemented. Downgrades can be performed manually by switching the active color.

server/docker-compose_web.yml

@@ -1,4 +1,7 @@
 x-common: &common
+  image: badbl0cks/pkmntrade-club:${IMAGE_TAG:-stable}
+  #image: ghcr.io/xe/x/httpdebug
+  #entrypoint: ["/ko-app/httpdebug", "--bind", ":8000"]
   restart: always
   env_file:
     - .env
@@ -6,31 +9,42 @@ x-common: &common
 services:
   web:
     <<: *common
-    image: ghcr.io/xe/x/httpdebug
-    entrypoint: ["/ko-app/httpdebug", "--bind", ":8000"]
-    #image: badbl0cks/pkmntrade-club:stable
+    environment:
+      - DEBUG=False
+      - DISABLE_SIGNUPS=True
+      - PUBLIC_HOST=${DOMAIN_NAME}
+      - ALLOWED_HOSTS=${DOMAIN_NAME},127.0.0.1
+      - DEPLOYMENT_COLOR=${DEPLOYMENT_COLOR:-blue}
+    labels:
+      - "enable_gatekeeper=true"
+      - "deployment.color=${DEPLOYMENT_COLOR:-blue}"
+      - "deployment.image_tag=${IMAGE_TAG:-stable}"
+    deploy:
+      mode: replicated
+      replicas: ${REPLICA_COUNT}
+    healthcheck:
+      test: ["CMD", "curl", "-f", "http://127.0.0.1:8000/health/"]
+      interval: 5s
+      timeout: 3s
+      retries: 2
+      start_period: 60s
+    stop_grace_period: 200s  # 20s buffer + 180s workers-kill-timeout
+    
+  celery:
+    <<: *common
     environment:
       - DEBUG=False
       - DISABLE_SIGNUPS=True
       - PUBLIC_HOST=pkmntrade.club
       - ALLOWED_HOSTS=pkmntrade.club,127.0.0.1
+      - DEPLOYMENT_COLOR=${DEPLOYMENT_COLOR:-blue}
     labels:
-      - "enable_gatekeeper=true"
-    deploy:
-      mode: replicated
-      replicas: 4
-    # healthcheck:
-    #   test: ["CMD", "curl", "-f", "http://127.0.0.1:8000/health"]
-    #   interval: 30s
-    #   timeout: 10s
-    #   retries: 3
-    #   start_period: 30s
-  # celery:
-  #   <<: *common
-  #   image: badbl0cks/pkmntrade-club:stable
-  #   environment:
-  #     - DEBUG=False
-  #     - DISABLE_SIGNUPS=True
-  #     - PUBLIC_HOST=pkmntrade.club
-  #     - ALLOWED_HOSTS=pkmntrade.club,127.0.0.1
-  #   command: ["celery", "-A", "pkmntrade_club.django_project", "worker", "-l", "INFO", "-B", "-E"]
+      - "deployment.color=${DEPLOYMENT_COLOR:-blue}"
+      - "deployment.image_tag=${IMAGE_TAG:-stable}"
+    command: ["celery", "-A", "pkmntrade_club.django_project", "worker", "-l", "INFO", "-B", "-E"]
+    stop_grace_period: 200s # match our longest stop_grace_period (currently web service is 200s)
+
+networks:
+  default:
+    name: pkmntrade-club_network
+    external: true