Adds API routes for managing roles and member role assignments.

New Endpoints POST/GET/PUT/DELETE /api/roles - CRUD for custom roles GET /api/roles/by-name/:name - Lookup role by name PUT/GET/DELETE /api/members/:userId/role - Manage member role assignments

Key Features Permission validation (can’t grant permissions you don’t have) Predefined role protection (admin, member, editor) Role deletion safeguards (can’t delete if assigned to members) /claim https://github.com/archestra-ai/archestra/issues/1446