Privacy-focused enhancements for user_status

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Is your feature request related to a problem? Please describe.
If the user_status app is enabled, it is "always-on" by default. While users can manually set their status to "Invisible/Appear offline," this approach lacks a privacy-first logic. Currently, a user can hide their own presence while still monitoring the status of everyone else. Furthermore, the "Opt-out" nature of the app (being visible until manually changed) is not ideal privacy wise.

Describe the solution you'd like

1. Reciprocal Privacy
   Introduce a personal setting to disable the user status. If a user chooses to have their status disabled, they should also be restricted from seeing the status of other users. This prevents "monitoring" and ensures fairness and privacy among users. (Basically the "Read-Receipt" Principle)
2. Global Opt-in
   Add an administrative toggle that allows the user status to be "disabled" for all users by default. Status tracking and visibility should only happen once a user actively opts-in via their personal settings.
   --
   Nice to have:
3. Group-based restrictions: An admin setting to restrict the user status capability to specific groups only. Only users of specified groups will have the possibility to see/enable the user status at all.
4. Granular Sharing: A personal setting allowing users to define who can see their status (e.g., "Only members of my groups" or "Specific users/groups").

Describe alternatives you've considered
The current "Invisible/Appear offline" toggle is a manual workaround but does not enforce reciprocity and does not solve the "Opt-out" issue for new accounts.

Additional context
Other collaboration platforms like Teams, Slack, or Mattermost also lack these privacy features. Nextcloud could be one of the first to deliver this kind of privacy settings.

The issue concerns the user_status app but names no files, tests, or entry points. First map the existing personal and administrative status settings; done requires an agreed scope and working privacy behavior, with the optional group-based and granular-sharing requests explicitly resolved.