- Rewrite post_list/submit schema (PHP + JS) with the reference theme's
field set, order, defaults and dependencies; topics fields excluded
- Map PostDisplay::get_submit_settings() and the FrontSubmit runtime to
the new keys without legacy fallback
- Guest submission follows the capability matrix; category required on
submit; pay limits read from the cash/points fieldset
- Drop dead front_submit_* settings, template branches and JS config
- Add submit settings reference contract test