Feature proposal: Custom Roles support with granular organization permissions

Hi maintainers, I would like to propose and validate a Custom Roles implementation for organization memberships in Vaultwarden, with granular permissions aligned to Bitwarden-style keys. Why this feature Organization authorization is currently mostly role-tier based (Owner/Admin/Manager/User). For many teams, this is too coarse and can force broader access than needed. The goal is to support least-privilege delegation, for example allowing someone to manage users or groups without full admin power. What is implemented • Database support: added a nullable permissions field on organization membership records (users_organizations), with migrations for sqlite, mysql, and postgresql. • Typed permission model: added an OrganizationUserPermissions structure and permission enum for these keys: accessEventLogs, accessImportExport, accessReports, createNewCollections, editAnyCollection, deleteAnyCollection, manageGroups, managePolicies, manageSso, manageUsers, mana…