Sync text zoom preference through the account instead of local settings

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.

scripts/ui/ccs_review.gd

@@ -40,6 +40,7 @@ func _ready() -> void:
 	status = Label.new(); Style.set_label(status, 14, Style.RED); row.add_child(status)
 	CCSService.request_failed.connect(_request_failed)
 	if not theme_service.theme_changed.is_connected(_on_theme_changed): theme_service.theme_changed.connect(_on_theme_changed)
+	if not CCSService.text_scale_changed.is_connected(_apply_text_scale): CCSService.text_scale_changed.connect(_apply_text_scale)
 
 func _study_label(region: String) -> RichTextLabel:
 	var label := RichTextLabel.new(); label.bbcode_enabled = true; label.fit_content = true; label.selection_enabled = true; label.set_meta("ccs_region", region); label.gui_input.connect(_text_input.bind(label)); return label