feat(enterprise): permission groups, access control

[icecrasher321]

Summary

Define permission groups to control what features and integrations team members can use.

Allowed Model Providers - Restrict which AI providers users can access (OpenAI, Anthropic, Google, etc.) Allowed Blocks - Control which workflow blocks are available Platform Settings - Hide Knowledge Base, disable MCP tools, or disable custom tools

Type of Change

• [x] New feature

Testing

Tested manually

Checklist

• [x] Code follows project style guidelines
• [x] Self-reviewed my changes
• [x] Tests added/updated and passing
• [x] No new warnings introduced
• [x] I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)