Add posterminal and posterminalcategory tables to control which categories
are visible on each POS terminal. The existence of a row in
posterminalcategory means the category is visible on that terminal.
Store methods:
- posterminal.list/upsert/delete - CRUD for terminals
- posterminal.setOn/setOff - toggle single category on a terminal
- posterminal.setOnAll/setOffAll - toggle all categories on a terminal
- posterminal.getCategoryPosterminalIds - internal, used by category tree
The category tree (getTreeForCompany) now includes a posterminalIds array
on each node listing which terminals have that category enabled.
Validates both source and target via resolveCategoryAccess so the new
parent must be a category of the same authorized company, and guards
against moving into a descendant (cycle). Assigns next sibling sort.
brand now carries a NOT NULL company_id (unique per (company_id, name))
with brand.list/upsert/delete backed by resolveCompanyAccess. Adds
companysetting key-value store (list/get/set/delete, frontend flag).
