Move unit tests from tests/unit/ to internal/ following Go conventions:
- tests/unit/queue/* -> internal/queue/* (dedup, filesystem_fallback, queue_permissions, queue_spec, queue, sqlite_queue tests)
- tests/unit/gpu/* -> internal/resources/* (gpu_detector, gpu_golden tests)
- tests/unit/resources/* -> internal/resources/* (manager_test.go)
Update import paths in test files to reflect new locations.
Note: GPU tests consolidated into resources package since GPU detection is part of resource management. Manager tests show significant new test coverage (166 lines).
