-- Per-user UI font scale (PERCENT of base; 100 = base). Persisted like `theme`/`language`
-- so an operator's chosen text size is restored on the next login from any booth. Additive
-- ALTER ADD COLUMN — backward-compatible; existing users default to 100 (base). The client
-- clamps to 80–160 in steps of 10. Printed tickets are unaffected (server-rendered).
ALTER TABLE `users` ADD `font_scale` integer DEFAULT 100 NOT NULL;