fix(config): align site base url defaults

docs/deployment.md

@@ -103,6 +103,13 @@ Required backend configuration:
 - email host, port, username, password, TLS settings, and sender address;
 - public site URL used to build confirmation and QR verification links.
 
+Local Docker convention:
+
+- use nginx as the public entrypoint at `http://localhost`;
+- set `SITE_BASE_URL=http://localhost`;
+- keep `DJANGO_CSRF_TRUSTED_ORIGINS` and browser-facing `CORS_ALLOWED_ORIGINS` aligned with that public URL;
+- if you publish nginx on a different port, update `SITE_BASE_URL` and trusted origins to the same host and port.
+
 Required database configuration:
 
 - database name;