Make DynamoDB Table Backup Schedule Configurable

[Basti110]

Describe the outcome you'd like

I would like the ability to configure the AWS Backup schedule within the AFT (Account Factory for Terraform) module via a Terraform variable, rather than having it hardcoded.

Specifically, I propose adding a new input variable (e.g., aft_backup_schedule) that defaults to the current hourly value but allows users to override it with a custom cron expression (e.g., daily or weekly) to better suit their operational requirements.

Is your feature request related to a problem you are currently experiencing? If so, please describe.

Currently, the backup schedule is hardcoded to cron(0 * * * ? *) (hourly) in modules/aft-account-request-framework/backup.tf. This rigidity creates the following issues:

Excessive Costs: Hourly backups generate high storage costs and significantly increase AWS Config recording costs due to the volume of resource changes.

Redundancy: Since point_in_time_recovery (PITR) is already active for every table in the stack, hourly snapshots are often unnecessary for many use cases.

Lack of Flexibility: Users cannot adjust the Frequency to match their specific RPO (Recovery Point Objective) or compliance standards.