fix: use entrypoint script for prod container startup

YAML folded block scalar (>) was preserving newlines for more-indented
continuation lines, so gunicorn received no arguments and defaulted to
binding on 127.0.0.1:8000. Replace with an explicit entrypoint script
so all args are passed correctly.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

docker-compose.prod.yml

@@ -2,17 +2,7 @@ services:
   web:
     build: app
     working_dir: /app
-    command: >
-      sh -c "python manage.py tailwind install --no-input &&
-             python manage.py tailwind build &&
-             python manage.py migrate --noinput &&
-             python manage.py collectstatic --noinput &&
-             gunicorn config.wsgi:application
-               --workers 3
-               --bind 0.0.0.0:8000
-               --access-logfile -
-               --error-logfile -
-               --capture-output"
+    command: /app/deploy/entrypoint.prod.sh
     env_file: .env
     environment:
       DJANGO_SETTINGS_MODULE: config.settings.production