feat: Implement dynamic Gatekeeper proxy and enhance service health monitoring

- **Implemented Dynamic Gatekeeper (Anubis) Proxy:**
  - Introduced Anubis as a Gatekeeper proxy layer for services (`web`, `web-staging`, `feedback`, `health`).
  - Added `docker-gen` setup (`docker-compose_gatekeeper.template.yml`, `gatekeeper-manager`) to dynamically configure Anubis instances based on container labels (`enable_gatekeeper=true`).
  - Updated HAProxy to route traffic through the respective Gatekeeper services.

- **Enhanced Service Health Monitoring & Checks:**
  - Integrated `django-health-check` into the Django application, providing detailed health endpoints (e.g., `/health/`).
  - Replaced the custom health check view with `django-health-check` URLs.
  - Added `psutil` for system metrics in health checks.
  - Made Gatus configuration dynamic using `docker-gen` (`config.template.yaml`), allowing automatic discovery and monitoring of service instances (e.g., web workers).
  - Externalized Gatus SMTP credentials to environment variables.
  - Strengthened `docker-compose_core.yml` with a combined `db-redis-healthcheck` service reporting to Gatus.
  - Added explicit health checks for `db` and `redis` services in `docker-compose.yml`.

- **Improved Docker & Compose Configuration:**
  - Added `depends_on` conditions in `docker-compose.yml` for `web` and `celery` services to wait for the database.
  - Updated `ALLOWED_HOSTS` in `docker-compose_staging.yml` and `docker-compose_web.yml` to include internal container names for Gatekeeper communication.
  - Set `DEBUG=False` for staging services.
  - Removed `.env.production` from `.gitignore` (standardized to `.env`).
  - Streamlined `scripts/entrypoint.sh` by removing the call to the no-longer-present `/deploy.sh`.

- **Dependency Updates:**
  - Added `django-health-check>=3.18.3` and `psutil>=7.0.0` to `pyproject.toml` and `uv.lock`.
  - Updated `settings.py` to include `health_check` apps, configuration, and use `REDIS_URL` consistently.

- **Streamlined deployment script used in GHA:**
  - Updated the workflow to copy new server files and create a new `.env` file in the temporary directory before moving them into place.
  - Consolidated the stopping and removal of old containers into a single step for better clarity and efficiency.
  - Reduce container downtime by rearranging stop/start steps.

server/docker-compose_gatekeeper.template.yml

@@ -0,0 +1,37 @@
+services:
+  {{ $all_containers := whereLabelValueMatches . "enable_gatekeeper" "true" }}
+  {{ $all_containers = sortObjectsByKeysAsc $all_containers "Name" }}
+
+  {{ range $container := $all_containers }}
+  {{ $serviceLabel := index $container.Labels "com.docker.compose.service" }}
+  {{ $containerNumber := index $container.Labels "com.docker.compose.container-number" }}
+  {{ $port := "" }}
+  {{ if eq $serviceLabel "web" }}
+    {{ $port = ":8000" }}
+  {{ end }}
+  {{ if eq $serviceLabel "web-staging" }}
+    {{ $port = ":8000" }}
+  {{ end }}
+  {{ if eq $serviceLabel "feedback" }}
+    {{ $port = ":3000" }}
+  {{ end }}
+  {{ if eq $serviceLabel "health" }}
+    {{ $port = ":8080" }}
+  {{ end }}
+  gatekeeper-{{ $serviceLabel }}-{{ $containerNumber }}:
+    image: ghcr.io/techarohq/anubis:latest
+    container_name: pkmntrade-club-gatekeeper-{{ $serviceLabel }}-{{ $containerNumber }}
+    env_file:
+      - .env
+    environment:
+      - TARGET=http://{{ $container.Name }}{{ $port }}
+    networks:
+      default:
+        aliases:
+          - pkmntrade-club-gatekeeper-{{ $serviceLabel }}
+          - gatekeeper-{{ $serviceLabel }}
+  {{ end }}
+networks:
+  default:
+    name: pkmntrade-club_default
+    external: true