Add `WithoutOverlapping` middleware to `DatabaseBackupJob` keyed by backup ID
with timeout-based lock expiry to prevent concurrent runs.
Mark long-running backup executions as failed when they exceed the stale
time threshold, and add periodic retention enforcement in
`CleanupInstanceStuffsJob` with cache-based throttling.
Also add float casts for retention max-storage fields on
`ScheduledDatabaseBackup` and comprehensive feature tests covering
overlap middleware, stale detection, casts, and retention behavior.
- Added functionality for users to request an email change, including generating a verification code and setting an expiration time.
- Implemented methods in the User model to handle email change requests, code validation, and confirmation.
- Created a new job to update the user's email in Stripe after confirmation.
- Introduced rate limiting for email change requests and verification attempts to prevent abuse.
- Added a new notification for email change verification.
- Updated the profile component to manage email change requests and verification UI.
