Critical fix: WorkersHandler was missing workService dependency, causing
500 errors when workers tried to fail tasks. This caused tasks to get
stuck in "running" state permanently.
Also adds:
- /work/tasks endpoint for debugging all tasks across projects
- List method to WorkQueue interface for admin views
- HTTP client tests for api_client.go and claudebox/client.go (48 tests)
- Split work.go DTOs into work_dto.go to stay under 500 lines
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>