Clean up and reorganize using/import statements across the solution. Remove unnecessary DTO imports from Application and Infrastructure layers, and ensure Contracts DTOs are only referenced in API and BlazorWebApp layers. No business logic is changed; these updates improve code organization, reduce coupling, and clarify architectural separation between layers.
Refactored code to use C# 12 collection expressions ([]) for initializing empty lists and dictionaries instead of the older constructors. This change modernizes and simplifies collection initialization across models, services, and API clients without altering any logic.
Introduce interfaces for all API clients and update dependency injection to use these interfaces. Refactor services and components to depend on abstractions instead of concrete implementations, improving testability and maintainability.
Add a private _cachedLayoutUser field to BandLayoutService and update EnsureLayoutUserAsync to cache the layout user value after first retrieval or generation. This avoids repeated localStorage calls and improves performance.
Introduce BandLayoutService and shared models to manage grid band layouts across components. Refactor CatalogsGrid and MassDataGrid to use the new service, removing duplicated layout logic. Update _Imports.razor and register the service in Program.cs for improved maintainability and code reuse.
