- Add 28 unit tests for SourceService (TEST-004)
- Test all CRUD operations
- Test validation logic
- Test error handling
- Test research functionality
- Add 13 integration tests for sources API (TEST-005)
- Test POST /sources endpoint
- Test GET /sources endpoint with filters
- Test DELETE /sources endpoint
- Test POST /sources/research endpoint
- Fix ValidationError signatures in SourceService
- Fix NotebookLMError signatures
- Fix status parameter shadowing in sources router
Coverage: 28/28 unit tests pass, 13/13 integration tests pass