Improves drag and drop functionality by refactoring column detection to use column bounds instead of dates.
This change enhances the accuracy and efficiency of determining the target column during drag operations.
It also removes redundant code and simplifies the logic in both the DragDropManager and AllDayManager.
Refactors all-day event drag and drop handling for improved accuracy and performance.
Introduces a shared `ColumnDetectionUtils` for consistent column detection.
Simplifies all-day conversion during drag, placing events in row 1 and calculating the column from the target date.
Implements differential updates during drag end, updating only changed events for smoother transitions.