Add cursor pagination to note listings

[ExtraToast]

What to build

Note listings paginate using the estate cursor convention rather than a bare limit.

The knowledge base is the collection most likely to grow without bound, and it currently offers a limit with no way to page past it — so a caller can only ever see the first N results.

Acceptance criteria

• Note listings accept a cursor and a limit and return a next cursor
• A caller can page through the entire collection
• Paging is stable while notes are being added
• The change matches the convention written down for the other paginated collections

Blocked by

• Adopt the ProblemDetail customizer and re-export the spec