Sentry monitoring, reading orders, and improved test coverage

Error monitoring - Sentry integration for automatic error detection and reporting across the platform.

Reading order improvements - universe reading orders now support expanding a series into individual books. Reading order audit entries appear on series and universe history pages.

Entity link suggestions - curators can now auto-detect entity names in description text and convert them to cross-references.

Test coverage improved from 68% to 86% across all thresholds.