fix: persist preview admin access

README.md

@@ -118,6 +118,25 @@ python manage.py ensure_superuser
 python manage.py runserver
 ```
 
+### Persistent local preview without Docker
+
+The local preview uses `instance/preview.sqlite3`, which survives server restarts and is
+ignored by Git. Put the preview admin credentials in `instance/preview_admin.env`
+(also ignored by Git):
+
+```text
+DJANGO_SUPERUSER_USERNAME=admin
+DJANGO_SUPERUSER_EMAIL=admin@localhost
+DJANGO_SUPERUSER_PASSWORD=your-local-password
+DJANGO_SUPERUSER_SYNC_PASSWORD=False
+```
+
+Then start the preview with `./run_preview.sh`. It applies migrations and ensures the
+admin account exists before starting the server. Existing passwords are preserved;
+set `DJANGO_SUPERUSER_SYNC_PASSWORD=True` for one start only if you intentionally
+need to reset the account password. This preview database is separate from the
+PostgreSQL database used by Docker and production.
+
 ## Management commands
 
 ```bash