Adds StoryDeckView projection, IBuildDeckRepository.GetStoryDecksByClass interface method,
and BuildDeckRepository implementation that loads StoryDeckEntry rows for a class, fetches
matching BuildDeckProductEntry card lists, and expands each card by Number into a flat
CardIdArray. TDD: 2 tests in StoryDeckRepositoryTests (expand + empty-class).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>