EAI-1141 update openbao script

[woojae-siloai]

This PR enhances the way managing Openbao secrets.

Problem
Previous OpenBao initialization had limitations:

• Hardcoded secret generation in bootstrap scripts
• Secrets only added automatically during first cluster-forge deployment
• Manual secret management with no ongoing automation
• Tight coupling between initialization and configuration
• No GitOps integration for secret definitions

Solution
Current branch resolves limitations through:

• Decoupling: Separated bootstrap initialization from ongoing secret management
• Automation: Added CronJob-based secret management running every 5 minutes
• GitOps Integration: Secret definitions now under sources/openbao-config/ so ArgoCD can watch and manage configuration changes
• Declarative Approach: Replaced hardcoded scripts with configurable SECRET_PATH|TYPE|VALUE|BYTES format

Changes
Implementation Changes:

• Converted sources/openbao-config/ to proper Helm chart structure
• Added openbao-secret-definitions.yaml with declarative secret format
• Created openbao-secret-manager-cronjob.yaml for automated management
• Added unified manage-secrets.sh script replacing hardcoded generation
• Added openbao-secret-manager-scripts ConfigMap with idempotent logic (checks if secret exists first, only creates if missing)
• Updated bootstrap process for multi-stage secret deployment

Documentation Changes

• Updated secrets-management-architecture.md to reflect automated system
• Added secret-management-user-guide.md for practical operations
• Added openbao-config-helm-chart.md for technical reference