Fix text zoom not actually syncing, and expose it in Settings

Two real gaps meant the account-synced zoom (from the previous
"sync through the account" change) never reached the screen:
_load_cache() updated AccountProfileService.preferences but never
emitted profile_changed, so question_player.gd/ccs_service.gd (already
built and listening before login even happens) never found out a
cached value had loaded. And nothing forced a server refresh
right after login - it only fired if the user happened to open the
profile/progress screen, so a fresh device/session had no path to
the true synced value at all.

main.gd now calls AccountProfileService.refresh() once per login
(not on every silent token refresh) so the real preferences GET
always runs right after signing in, on any device.

Also added Question bank/CCS case text size steppers to the Settings
screen next to dark mode, per user request, reusing the same
AccountProfileService/CCSService plumbing as the in-screen A-/A+
buttons.

scripts/ui/main.gd

@@ -5,6 +5,7 @@ const Brand := preload("res://scripts/ui/medmind_style.gd")
 const NavigationRoutes := preload("res://scripts/ui/navigation_routes.gd")
 
 var screens := {}
+var _account_profile_synced := false
 var header_panel: PanelContainer
 var header_title: Label
 var environment_badge: Label
@@ -755,6 +756,12 @@ func open_legal_document(kind: String) -> void:
 
 func _on_auth_changed() -> void:
 	_refresh_header_controls()
+	if AuthState.is_logged_in:
+		if not _account_profile_synced:
+			_account_profile_synced = true
+			AccountProfileService.refresh()
+	else:
+		_account_profile_synced = false
 	if AuthState.is_logged_in and AuthState.requires_legal_acceptance and current_screen_name not in ["login", "legal_consent"]:
 		show_screen("legal_consent")