Schema versioning

Features

• Schema versioning with diff view in the admin panel.
• Per-environment promotion: dev → staging → prod, with one-click rollback.
• Audit log filters by entity + actor + field.

Improvements

• Faster planner agent on large prompts (~30% reduction in latency).
• Admin table virtualization for 50k+ rows.

Fixes

• RBAC matrix could not save multi-line role names.
• Stripe webhook handler retried twice on 5xx.

Breaking changes

• mango deploy --target now requires a workspace flag for multi-project repos.