feat: Implement Category, Item, UOM, Vendor, and Warehouse services with CRUD operations

- Added CategoryService for managing categories with listing, tree structure, and creation functionalities.
- Introduced ItemService for item management, including listing, detail retrieval, creation, updating, and status management.
- Created UomService for handling unit of measure operations, including listing and creation.
- Developed VendorService for vendor management, supporting listing, detail retrieval, creation, updating, and status management.
- Implemented WarehouseService for warehouse and bin management, including listing warehouses, creating warehouses, and managing bins within warehouses.
- Added interfaces for each service to define the contract for service implementations.
- Generated Entity Framework Core model snapshot for database migrations.

Backend/ERPCore/Program.cs

@@ -1,8 +1,11 @@
+using System.Text.Json.Serialization;
 using ERPCore.Infra.Auth;
 using ERPCore.Infra.Persistence;
 using ERPCore.Infra.UoW;
 using ERPCore.Repositories;
 using ERPCore.Repositories.Interfaces;
+using ERPCore.Services;
+using ERPCore.Services.Interfaces;
 using ERPCore.System.Errors;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.OpenApi;
@@ -15,7 +18,9 @@ builder.Host.UseSerilog((ctx, cfg) => cfg
     .ReadFrom.Configuration(ctx.Configuration)
     .WriteTo.File("logs/erpcore-.log", rollingInterval: RollingInterval.Day));
 
-builder.Services.AddControllers();
+// Controllers + JSON: serialize enums as their string names (docs/11 §8, camelCase).
+builder.Services.AddControllers()
+    .AddJsonOptions(o => o.JsonSerializerOptions.Converters.Add(new JsonStringEnumConverter()));
 
 // EF Core + PostgreSQL
 builder.Services.AddDbContext<ErpDbContext>(o =>
@@ -36,6 +41,13 @@ builder.Services.AddScoped<ICurrentUser, CurrentUser>();
 builder.Services.AddScoped<IUnitOfWork, UnitOfWork>();
 builder.Services.AddScoped(typeof(IRepository<>), typeof(Repository<>));
 
+// Master-data services (docs/11 §2)
+builder.Services.AddScoped<IItemService, ItemService>();
+builder.Services.AddScoped<IUomService, UomService>();
+builder.Services.AddScoped<ICategoryService, CategoryService>();
+builder.Services.AddScoped<IVendorService, VendorService>();
+builder.Services.AddScoped<IWarehouseService, WarehouseService>();
+
 // Health checks (EF Core DB)
 builder.Services.AddHealthChecks().AddDbContextCheck<ErpDbContext>();