fix(start): allow skipping collectstatic via DISABLE_COLLECTSTATIC env var

Deployments that serve static files from an external CDN (e.g. Netlify) do
not need Django's `collectstatic` to run on container boot. When the
configured `STATICFILES_STORAGE` backend is unreachable, `collectstatic`
can hang indefinitely on a network call, blocking gunicorn from starting
and causing 502 Bad Gateway responses upstream until the container is
killed and recreated.

This adds an opt-in env var (`DISABLE_COLLECTSTATIC=1`) that skips the
step entirely in `compose/production/django/start`. Default behaviour
(running `collectstatic`) is unchanged.

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

Author: mihow

compose/production/django/start

@@ -4,7 +4,11 @@ set -o errexit
 set -o pipefail
 set -o nounset
 
-python /app/manage.py collectstatic --noinput
+if [ "${DISABLE_COLLECTSTATIC:-0}" = "1" ]; then
+    echo "Skipping collectstatic (DISABLE_COLLECTSTATIC=1)"
+else
+    python /app/manage.py collectstatic --noinput
+fi
 
 # Gunicorn natively reads WEB_CONCURRENCY as its --workers default.
 # If not set, default to CPU core count.