The protected bool bandEditorExpanded, which tracked the expansion
state of the band editor, has been removed from BandGridBase<TItem>
as it is no longer used. This helps clean up unused state from
the component.
Introduced an abstract base class BandGridBase<TItem> to centralize banded grid functionality in Blazor apps using DevExpress. This class manages band layouts, column definitions, user-specific layout persistence, grid size modes, and rendering logic. It integrates with BandLayoutService for layout storage and retrieval, and is intended for inheritance by specific grid components.