Enable generating service-record documents for a single task on /putni-nalozi/racuni while preserving existing full work-order export.
- Backend service-records PDF/DOCX endpoints now accept optional task_id and validate the task belongs to the selected work order.
- Document builders support scoped task lists, and per-task downloads use task-specific filenames.
- Frontend task cards now include per-task PDF/DOCX actions, while top-level buttons are clarified as exporting all service records.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>