Role-based access control enforcement and roles dashboard

This release adds RBAC enforcement for projects (behind a feature flag) and introduces a dashboard for assigning roles.

Features

• RBAC enforcement for projects #2005 - Added role-based access control enforcement to projects, gated behind a feature flag. (Author: @tgmendes)
• Roles assignment dashboard #2078 - Added a feature-flagged dashboard for assigning roles to organization members. (Author: @qstearns)
• Dialog component for MCP server deletion #2076 - Replaced the browser confirm() dialog with a proper Dialog component for MCP server deletion, improving the user experience. (Author: @alx-xo)

Bug fixes

• Fix OAuth validation checks #2080 - Fixed an issue with OAuth validation checks when tools have no security annotations, ensuring toolset-level OAuth is checked correctly. (Author: @tgmendes)
• Fix custom domain verification on transient errors #2047 - Fixed custom domain verification to fail fast on transient database errors instead of incorrectly creating a new domain record. (Author: @bflad)