Backup CronJob should use DevWorkspaceOperatorConfig `imagePullPolicy`

[rohanKanojia]

Description

The backup CronJob controller hardcodes imagePullPolicy: Always on the backup container in createBackupJob (controllers/backupcronjob/backupcronjob_controller.go). It does not use config.workspace.imagePullPolicy from DevWorkspaceOperatorConfig, unlike other workspace-related auxiliary containers.

devworkspace-operator/controllers/backupcronjob/backupcronjob_controller.go

Line 418 in 113b402

ImagePullPolicy: "Always",

During backup load tests, backup Jobs can fail with registry rate limiting when many Jobs pull the same image on every run:

Failed to pull image "registry.redhat.io/devworkspace/devworkspace-project-backup-rhel9@sha256:...": pull QPS exceeded
Warning  Failed  kubelet  Error: ErrImagePull

Acceptance criteria

• Backup Job container imagePullPolicy is taken from resolved DevWorkspaceOperatorConfig config.workspace.imagePullPolicy.
• When the field is unset, behavior matches the operator default (Always).
• Unit test verifies backup Job spec reflects a non-default imagePullPolicy (e.g. IfNotPresent).
• Documented or verified that setting IfNotPresent reduces repeated pulls and mitigates registry QPS limits under backup load.