feat(R07): task repository, schedule calculator, Qt clock adapter, task/AI-planner services

Team Hoa, EPIC R07 (Scheduling & Workflow Runtime) - Team Hoa scope only
(R07-T01 -> T05; R07-T06 Co4EWorkflowService is Team Nam's).

- R07-T01: infrastructure/persistence/json/task_repository_impl.py wraps
  core/tasks.py's CRUD; core/tasks.py::save_task now writes through
  atomic_write.write_json (same durability fix as R06-T02, save_task was
  still doing a plain write_text).
- R07-T02: domain/tasks/schedule_calculator.py::ScheduleCalculator - the
  cron/interval/daily/weekly/monthly due-time math extracted from
  core/tasks.py, pure Python with is_holiday/make_cron injected so domain/
  never imports core (ADR-001 I2). core/tasks.py keeps its old function
  names as thin wrappers so every existing caller is unchanged. This was
  previously untested; now has its own unit suite.
- R07-T03: infrastructure/qt/qt_scheduler_clock.py::QtSchedulerClock wraps
  the QTimer TaskScheduler used to own directly, injected via a new
  `clock=` constructor param (defaults to a real one). Originally planned
  at platform/qt/... ; moved after confirming that name shadows the
  stdlib platform module (used by core/windows_sandbox_vm.py,
  core/appcontainer_sandbox.py) whenever the repo root is on sys.path.
  tests/fakes/fake_clock.py lets scheduler dispatch be tested tick-by-tick
  with no Qt event loop.
- R07-T04: application/scheduling/task_application_service.py centralizes
  run_now/duplicate/pause/delete/bulk_delete and the Kanban drag-drop
  business rules (move_to_status), currently only reachable by driving
  the real ui/schedule_task_tab.py widget.
- R07-T05: application/scheduling/ai_task_planner_service.py wraps
  core/ai_task_planner.py::plan_tasks and core/task_import.py::import_tasks
  as a seam, plus the attachment-stamping step that used to only exist
  inside the AI-create dialog's worker closure.

pytest: 328 pass (same 4 pre-existing failures as the R05/R06 baseline,
unrelated to this work - see docs/refactor/BaoCao_TeamHoa_R05_R06.md).
scripts/check_imports.py: PASS.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

docs/refactor/Refactoring_Checklist.md

@@ -209,18 +209,18 @@
 * **Team chịu trách nhiệm**: 🟢 **Team Hoa** (Task Scheduling) + 🟣 **Team Nam** (Co4E Workflows)
 * **Mục tiêu**: Tách `TaskRepository` và `ScheduleCalculator` khỏi `QTimer` trong `core/task_scheduler.py#L20`; xây dựng `TaskApplicationService` và `Co4EWorkflowService`.
 
-- [ ] **R07-T01 (Team Hoa)**: Tách `TaskRepository` lưu trữ JSON độc lập khỏi `core/tasks.py` ➔ `infrastructure/persistence/json/task_repository_impl.py`  
-  *Start: `____-__-__ __:__` | End: `____-__-__ __:__`*
-- [ ] **R07-T02 (Team Hoa)**: Xây dựng `ScheduleCalculator` tính due-time / cron độc lập ➔ `domain/tasks/schedule_calculator.py`  
-  *Start: `____-__-__ __:__` | End: `____-__-__ __:__`*
-- [ ] **R07-T03 (Team Hoa)**: Xây dựng `QtSchedulerClock` adapter (tách `TaskScheduler` khỏi `QTimer`) ➔ `platform/qt/qt_scheduler_clock.py`  
-  *Start: `____-__-__ __:__` | End: `____-__-__ __:__`*
-- [ ] **R07-T04 (Team Hoa)**: Xây dựng `TaskApplicationService` (Pure Python) điều phối chạy, sao chép, dừng, xóa task ➔ `application/scheduling/task_application_service.py`  
-  *Start: `____-__-__ __:__` | End: `____-__-__ __:__`*
-- [ ] **R07-T05 (Team Hoa)**: Xây dựng `AiTaskPlannerService` hỗ trợ tạo / import task bằng AI ➔ `application/scheduling/ai_task_planner_service.py`  
-  *Start: `____-__-__ __:__` | End: `____-__-__ __:__`*
+- [x] **R07-T01 (Team Hoa)**: Tách `TaskRepository` lưu trữ JSON độc lập khỏi `core/tasks.py` ➔ `infrastructure/persistence/json/task_repository_impl.py`  
+  *Start: `2026-08-27 16:05` | End: `2026-08-27 16:14`*
+- [x] **R07-T02 (Team Hoa)**: Xây dựng `ScheduleCalculator` tính due-time / cron độc lập ➔ `domain/tasks/schedule_calculator.py`  
+  *Start: `2026-08-27 16:14` | End: `2026-08-27 16:26`*
+- [x] **R07-T03 (Team Hoa)**: Xây dựng `QtSchedulerClock` adapter (tách `TaskScheduler` khỏi `QTimer`) ➔ `infrastructure/qt/qt_scheduler_clock.py` (đổi so với plan gốc `platform/qt/...` — xem báo cáo)  
+  *Start: `2026-08-27 16:26` | End: `2026-08-27 16:47`*
+- [x] **R07-T04 (Team Hoa)**: Xây dựng `TaskApplicationService` (Pure Python) điều phối chạy, sao chép, dừng, xóa task ➔ `application/scheduling/task_application_service.py`  
+  *Start: `2026-08-27 16:47` | End: `2026-08-27 17:02`*
+- [x] **R07-T05 (Team Hoa)**: Xây dựng `AiTaskPlannerService` hỗ trợ tạo / import task bằng AI ➔ `application/scheduling/ai_task_planner_service.py`  
+  *Start: `2026-08-27 17:02` | End: `2026-08-27 17:14`*
 - [ ] **R07-T06 (Team Nam)**: Xây dựng `Co4EWorkflowService` (Pure Python) quản lý định nghĩa và thực thi Co4E từ `core/co4e_run_manager.py` ➔ `application/workflows/co4e_workflow_service.py`  
-  *Start: `____-__-__ __:__` | End: `____-__-__ __:__`*
+  *Start: `____-__-__ __:__` | End: `____-__-__ __:__`* (ngoài phạm vi Team Hoa)
 
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