Add settings roles page (#9940)

## Context
This PR introduces a new Roles settings page, accessible through the
settings menu when the isPermissionsEnabled feature flag is enabled. The
page provides a foundation for managing user roles within the workspace.

This is not fetching the roles from the BE for now and will be done in a
followup PR.

packages/twenty-server/src/engine/core-modules/feature-flag/enums/feature-flag-key.enum.ts

@@ -16,4 +16,5 @@ export enum FeatureFlagKey {
   IsBillingPlansEnabled = 'IS_BILLING_PLANS_ENABLED',
   IsRichTextV2Enabled = 'IS_RICH_TEXT_V2_ENABLED',
   IsNewRelationEnabled = 'IS_NEW_RELATION_ENABLED',
+  IsPermissionsEnabled = 'IS_PERMISSIONS_ENABLED',
 }