Add no-code policy editor in admin UI

[haasonsaas]

Context

Gate requires writing raw Rego to create policies. This blocks security teams who are not developers from owning policies directly. Formal.ai offers a no-code policy editor — this is a key adoption differentiator for the security-team buyer persona.

Proposal

Build a visual policy builder in the embedded admin UI that emits valid Rego:

• Rule wizard UI: structured form for common patterns (allow/deny by role, IP range, time window, query type, resource)
• Conditional builder: drag-and-drop or form-based condition chains (AND/OR/NOT)
• Preview pane: shows the generated Rego so engineers can review/tweak
• Round-trip editing: policies created in the UI can be edited as raw Rego, and simple Rego can be loaded back into the visual editor
• Does NOT replace Rego — sits on top of it. Power users still write raw Rego.

Acceptance Criteria

• Visual policy builder generates valid Rego for at least 5 common patterns
• Generated policies pass Gate's existing Rego v1 strict validation
• Preview shows generated Rego before saving
• Policies created visually go through the same draft → dry_run → active lifecycle
• Non-technical user can create "block DDL for non-admin roles" without writing code