Run collectstatic at container startup

The Docker volume for staticfiles persists across deploys, so
baked-in static files from the image get overridden by the old
volume contents. Running collectstatic at startup ensures the
volume always has the latest files.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: mattstratton

docker-compose.prod.yml

@@ -2,7 +2,8 @@ services:
   web:
     image: ghcr.io/devopsdays/devopsdays-web-app:latest
     command: >
-      sh -c "python manage.py migrate --noinput &&
+      sh -c "python manage.py collectstatic --noinput &&
+             python manage.py migrate --noinput &&
              gunicorn config.wsgi:application --bind 0.0.0.0:8000 --workers 3 --timeout 120"
     volumes:
       - media_files:/app/media