chore: rename manager/member to administrator (#11542)

# Which Problems Are Solved

As part of the naming consistency initiative, the terms `Manager`,
`Member` and other similar terms that are used in the context of an
administrator are replaced by `Administrator` in the UI and
documentation.

# How the Problems Are Solved

By replacing the following terms with Administrator / Administrator
Roles in docs, Console UI, and guides.

- Manager
- Add Manager
- Add a Manager
- Administrator (used as a person type)
- Membership
- Member grants

# Additional Changes
minor grammatical edits in the docs

# Additional Context
- Closes https://github.com/zitadel/zitadel/issues/11291

---------

Co-authored-by: Marco A. <[email protected]>

apps/docs/content/concepts/structure/users.mdx

@@ -25,9 +25,9 @@ The main difference between users and service accounts is the type of credential
 
 Learn how to [use service accounts](/guides/integrate/service-accounts/authenticate-service-accounts) with ZITADEL.
 
-### Managers
+### Administrators
 
-Any user or service account can be given a [Manager](/concepts/structure/managers) role.
+Any user or service account can be assigned an [Administrator](/concepts/structure/administrators) role.
 A user with an administrator role is not only an end-user of ZITADEL but can also manage certain aspects of ZITADEL itself.
 
 ### Federated users
@@ -59,7 +59,7 @@ Consider this general recommendation as a starting point:
 - Create one organization ("default organization") for your own company
 - Configure projects and applications in the default organization
 - Structure users in organizations based on common domains that are self-managed (eg, company)
-- Grant your projects to the organizations, allow Managers to give granted roles to their users
+- Grant your projects to the organizations, allow Administrators to give granted roles to their users
 
 You might want to adjust this general setup based on your [scenario](/guides/solution-scenarios).