Remove duplicate authorization data from Zitadel IdP. NetBird now stores
all authorization data (account membership, invite status, roles) locally,
while Zitadel only stores identity information (email, name, credentials).
Changes:
- Add PendingInvite field to User struct to track invite status locally
- Simplify IdP Manager interface: remove metadata methods, add GetAllUsers
- Update cache warming to match IdP users against NetBird DB
- Remove addAccountIDToIDPAppMeta and all wt_* metadata writes
- Delete legacy IdP managers (Auth0, Azure, Keycloak, Okta, Google
Workspace, JumpCloud, Authentik, PocketId) - only Zitadel supported
