Local user://settings.cfg meant zoom level didn't follow a student
across devices/browsers. Question bank and CCS text scale now live on
the user's study profile in Mongo (QuestionTextScale/CcsTextScale),
synced through a new PUT /api/profile/me/text-scale endpoint and the
existing preferences GET/cache already used for study preferences.
Both question_player.gd and ccs_service.gd read the synced value at
startup and react to AccountProfileService.profile_changed so a value
pulled down after login (or changed from another session) applies
without a restart. Backend validates the 0.85-1.35 range and updates
only the field(s) provided via a targeted $set, so it can't clobber
the other scale or the unrelated study-profile preferences.
hz