Fix: Remove disabled users from the lookup server

[rikled]

Deactivated accounts were never removed from the lookup server: batchUpdate() re-pushed them on every cron run and nothing reacted to disable events, so disabled users kept showing up in federated share contacts.

This change:

• skips disabled users in batchUpdate() and batches their removal,
• hardens updateUser() to remove rather than re-add a disabled user,
• adds a UserChanged listener so enable/disable is reflected immediately instead of waiting for the next cron run,
• adds unit tests covering the add/remove routing.

🤖 AI (if applicable)

• The content of this PR was partly or fully generated using AI

Assisted-by: Claude Code:Opus 4.8

[artonge]

Might be similar to #215
cc @cristianscheid

[cristianscheid]

Might be similar to #215 cc @cristianscheid

Yes, looking at the changes it accomplishes the same thing as #215. Major difference is how PRs handle existing disabled users on lookup server:

• this PR uses batchUpdate() method, which is called on a cron job
• #215 removes the user at login time, if the disabled user attempts to authenticate, rather than on a schedule

[cristianscheid]

Following up on this topic, I've updated #215 to include the changes proposed by this PR for the batchUpdate() method.

Changes on #215 were included on this commit. I think this makes sense because only removing disabled users at login time would leave their records on the lookup server until they actually attempt to log in. Including this change means the cron job will eventaually clean up any leftover disabled users.

@rikled thanks for the contribution, really appreciated! Since now both PRs are more in sync, I'll close this one in favor of the previously open.

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