Fixes#997
- Add Task.STATUS.CANCELLED to exclusion list in fetchOverdueTasks()
- Add Task.STATUS.CANCELLED to exclusion list in fetchTasksDueToday()
- Cancelled tasks now properly filtered out from Today page sections
- All existing tests pass
Added proper ordering configuration (separate: true and order clause)
to subtask queries in query-builders.js. This ensures subtasks are
always returned in the correct order based on the 'order' field and
'created_at' timestamp, preventing the intermittent reordering bug
that occurred after checking subtasks as complete and reloading.
Fixes#921
