test(backup): round-trip every account setting through a real restore

Fill every User column on the source account, export through the streaming
writer, recreate the account with credentials of its own, restore through the
route, and compare: each setting column must come back with the value it left
with, and every identity, credential and bookkeeping column must still hold
the target's value. The section in the file is checked to carry nothing but
setting columns.

src/lib/export/backup-plan.ts

@@ -934,9 +934,6 @@ export const USER_COLUMN_BACKUP_CLASS = {
   Record<string, "SETTING" | "CREDENTIAL" | "IDENTITY" | "OPERATIONAL">
 >;
 
-export type UserColumnBackupClass =
-  (typeof USER_COLUMN_BACKUP_CLASS)[keyof typeof USER_COLUMN_BACKUP_CLASS];
-
 /** The `User` columns the `accountSettings` section carries. */
 export type AccountSettingColumn = {
   [