Leave sets I already approved out of the Awaiting me queue #2671

Part of #2422 (F-DSK). Found in the review of #2668 (RTE-05 approvals). Not introduced by it: #2562 deferred this until approvals were recorded, and they now are.

The "Awaiting me" queue still lists a set the signed-in person has already approved. With a set that needs 2 approvals, the first reviewer approves it, and the set stays in their queue. "Next in queue" can then land them on a set where Approve is hidden. The comment at src/FluentCMS.Core/Desk/DeskQueues.cs and the desk text in Desk.razor both say the queue will filter once approvals are recorded.

Scope

• "Awaiting me" leaves out sets the current person has approved. Its count and the MCP desk tools follow the same rule.
• "Next in queue" skips those sets as well.

Acceptance

• After a person approves a set that needs 2 approvals, the set is no longer in their "Awaiting me" queue or its count. It still appears for another person.
• "Next in queue" after that approval opens the next set the person has not approved.
• All of the above passes on SQLite and PostgreSQL.