Phase 6 test infrastructure (6.1, 6.2, 6.5): - Fix .coveragerc source path (src -> .) - Fix pre-existing test failure (patch target + method rename) - Add 52 database layer tests covering CRUD, junction table tags, search, pagination, statistics, image linking, and edge cases - Add GitHub Actions CI workflow (Python 3.10-3.12) - Total: 61 tests, all passing