Book covers, search, and testing

Book covers - cover images now come from ISBNdb with multiple size options. Select your preferred cover during ISBN lookup, and it's stored for fast page loads without API calls.

Curator search - search across all entity types from the dashboard header for quick navigation.

Author attribution - duplicate detection for similar author names, and attribution sources displayed on public author pages.

Testing - comprehensive test suite expansion with in-memory SQLite test database, API mocking infrastructure, and coverage improved to ~71%.

Form improvements - automatic focus on validation errors, character counters, warn-but-allow duplicate name handling, and "Create another" links after entity creation.

Book covers - cover images now come from ISBNdb with multiple size options. Select your preferred cover during ISBN lookup, and it's stored for fast page loads without API calls.

Curator search - search across all entity types from the dashboard header for quick navigation.

Author attribution - duplicate detection for similar author names, and attribution sources displayed on public author pages.

Testing - comprehensive test suite expansion with in-memory SQLite test database, API mocking infrastructure, and coverage improved to ~71%.

Form improvements - automatic focus on validation errors, character counters, warn-but-allow duplicate name handling, and "Create another" links after entity creation.