Add tooltips on server status indicators for federated sharing / tidy up Federated/Federation settings section(s)

Description

• I just learnt that you DON'T need green status in federation for the servers to actually federate.
• Green status is just to symbolize successful exchange of contact lists which means you can just add the usernames yourself in the search bar without the suggestions and it would work.
• This is an important and relieving discovery for me, because I typically waste a lot of time when trying to get green status with two servers to test federated stuff.

Steps to reproduce

See notes on federating : https://docs.nextcloud.com/server/latest/admin_manual/configuration_files/federated_cloud_sharing_configuration.html

Expected behavior

• I think hovering over the status icons should explain what is possible or what the dots mean right in the UI
• I addition to existing overview text, users can be directed to hover over the status icon to learn more about the current status.

cc: @nextcloud/d

Nextcloud Server version

master

Operating system

None

PHP engine version

None

Web server

None

Database engine version

None

Is this bug present after an update or on a fresh install?

None

Are you using the Nextcloud Server Encryption module?

None

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

No response

List of activated Apps

No response

Nextcloud Signing status

No response

Nextcloud Logs

No response

Additional info

No response

Start with the federated cloud sharing configuration documentation linked in the issue, then locate the server-status indicators and Federated/Federation settings entry points it describes. Confirm the meaning of each status and define the tooltip and overview wording; done means the UI explains each indicator and whether federation can work without green status.