Retrieve aggregated citation statistics for an author.

Retrieve aggregated citation statistics for an author without fetching all papers.

Returns:

• tally: How this author's papers are cited by others (supporting, contrasting, mentioning counts)
• citingTally: How this author's papers cite other works (supporting, contrasting, mentioning counts)
• totalPapers: Total number of papers by this author

This endpoint performs the aggregation server-side, eliminating the need for clients to fetch all papers in chunks and aggregate locally.