- Add product_name, product_version to top-level keys table
- Clarify version fields are informational and ignored at import
- Fix users: link to Computing Password Hashes section, detail limits format
- Fix vhosts: add tracing field, move description/tags/default_queue_type
  inside metadata, document backward-compatible direct properties
- Fix queues: add exclusive field, document that type is export-only and
  x-queue-type argument must be used at import time (admonition added)
- Clarify "at import time" for all boolean defaults
- Add properties_key to bindings
- Update minimal example to use x-queue-type argument

- Users: add plaintext password field as alternative to password_hash,
  mark both as optional (either one should be provided)
- Bindings: routing_key is optional (defaults to empty string),
  common for fanout and headers exchange bindings
- Queues: remove exclusive field (no practical use in definitions),
  fix contradiction in admonition (remove type from fallback sentence)
- Vhosts: use neutral example without default_queue_type on /

- Note that product_name/product_version are only in management plugin
  exports, not in rabbitmqctl output
- Document the fixed import order (users, vhosts, permissions, exchanges,
  topic permissions, global parameters, policies, parameters, queues,
  bindings) so users know ordering in the JSON file does not matter