Introduce MassData feature with new API endpoints for querying and upserting records by customer name. Add DTOs, AutoMapper profile, MediatR CQRS handlers, repository pattern, and MassDataDbContext. Register new services in DI and add MassDataConnection to configuration. Upsert uses stored procedure. Enables full CRUD for Massdata via dedicated API.
Refactored IRepository<T> and ICatalogRepository to reside in the DbFirst.Application layer instead of Domain. Updated namespaces, using statements, and all references in services and handlers. Adjusted csproj dependencies to reflect the new structure. Updated comments to clarify Clean Architecture rationale and improved separation of concerns.
