Adds IndexedDB and operation queue for robust offline synchronization
Introduces SyncManager to handle background data synchronization
Supports local event operations with automatic remote sync queuing
Enhances application reliability and user experience in low/no connectivity scenarios
Refactors the event layout and stacking logic based on review feedback.
This includes:
- Merging conflicting event groups to prevent inconsistencies.
- Implementing minimal stack level assignment using a min-heap.
- Consolidating styling and using DateService for drag operations.
- Adding reflow after drag and drop.
- Improving the column event filtering to include events overlapping midnight.
- Ensuring explicit sorting of events for grid layout.
Introduces a 3-phase algorithm in `EventStackManager` for dynamic event positioning. Groups events by start time proximity to determine optimal layout.
Optimizes horizontal space by using side-by-side grid columns for simultaneous events and allowing non-overlapping events to share stack levels. Supports nested stacking for late-arriving events within grid columns.
Includes comprehensive documentation (`STACKING_CONCEPT.md`) and a visual demonstration (`stacking-visualization.html`) to explain the new layout logic. Updates event rendering to utilize the new manager and adds extensive test coverage.
