Workspace defaults settings page

[AlexejPenner]

Summary

Admin-facing settings page for configuring workspace-level defaults: default deploy stack and default artifact store for local runs.

Requirements

• Settings page accessible from workspace settings (admin only)
• Default deploy stack: dropdown/selector from available stacks in the workspace
• Default artifact store: configuration input (details TBD pending open question resolution on path-based vs named component)
• Clear explanation of what these defaults do and how they're overridden
• Save/reset actions

Design Considerations

• Admin-only page — non-admins should see the current defaults (read-only) but not modify them
• Consider showing the precedence chain visually: "These defaults are used when no stack is specified in .deploy(). Users can override via env var, pyproject.toml, or explicit stack= argument."

Acceptance Criteria

• Admin can set default deploy stack
• Admin can set default artifact store
• Non-admin can view but not modify
• Clear explanation of precedence
• Settings persist and are picked up by SDK/CLI

Dependencies

• Depends on: Workspace-level default stack and artifact store configuration zenml#4732 (ZB-02), zenml-io/kitaru-test-prototypes#38 (FE-00: Design)