Enable scheduled ClickHouse backups across the job, API, and UI, and
guard unsupported database types via isBackupSolutionAvailable().
Convert Stripe subscription sync from a job to an action with clearer
discrepancy resolution, and add cloud:export-users plus
cloud:cleanup-unverified-users with tests.
Add polymorphic volume backup scheduling for persistent volumes and directories, expose schedule management via API, and reorganize backup configuration and execution views.
