[EPIC](greenhouse): Admin Area - Clusters list and details

[edda]

Description

Implement a modern Cluster management UI in Greenhouse, replacing the legacy with the new admin interface patterns. This will provide Cluster Admins, On-Callees, Plugin Developers, and Org Admins with a consistent, filterable view of clusters and their health, deployed plugins, and metadata.

Objectives

• Provide a unified cluster list view with filtering, searching, and status indicators
• Enable drill-down into cluster details including metadata, conditions, deployed plugins, and node health
• Align with existing PluginPreset UI patterns for consistency

Acceptance Criteria

• Cluster List view displays all clusters with status, name, K8s version, message, and connectivity type
• Cluster List is searchable and filterable by labels (default: owned-by)
• Cluster List shows total count and failing cluster count
• Cluster Detail view shows name, age, K8s version, connectivity, labels, annotations, conditions
• Cluster Detail shows deployed plugins with state and navigation to Plugin Instance Detail
• Cluster Detail shows node status (x/y ready) with appropriate color coding
• Cluster Detail includes raw YAML view
• Legacy cluster UI is deprecated/removed

Tasks

See Sub-issues section

Dependencies

None

Additional Notes

https://codi.eu-nl-1.cloud.sap/greenhouse-cluster-ui#UIs