[Improvement] Redundant Annotation Setup During Cluster Restoration

[shanshanying]

Context

When restoring a cluster from a backup, users are required to manually specify the kubeblocks.io/restore-from-backup annotation in the cluster CR.
However, certain fields within this annotation (e.g., EncryptedSystemAccount) appear to duplicate information already stored in the backup object's kubeblocks.io/encrypted-system-accounts annotation.

Problem

The current implementation forces users to:

• Manually copy system account details from the backup's annotation

• Maintain consistency between two separate annotations

But this creates unnecessary complexity and is error-prone.

Proposed Improvement

Automatically inherit EncryptedSystemAccount, if not specified, from the backup's kubeblocks.io/encrypted-system-accounts annotation during restoration, eliminating manual setup of redundant fields.