feat: Add new services and interfaces for GRN, Purchase Return, Reason Code, Reorder, Stock, and Transfer functionalities

- Implemented IGrnService for managing goods receipts including retrieval, creation, and confirmation.
- Created IPurchaseReturnService for handling purchase return operations.
- Added IReasonCodeService for managing reason codes with listing and creation capabilities.
- Developed IReorderService for fetching reorder alerts and creating suggested requisitions.
- Introduced IStockMutator for applying stock changes and posting ledger entries.
- Established IStockService for stock inquiries, ledger retrieval, and valuation.
- Created ITransferService for managing inter-warehouse transfers including dispatch and receiving operations.
- Implemented PurchaseReturnService to handle purchase return logic and stock adjustments.
- Developed ReasonCodeService for listing and creating reason codes.
- Created ReorderService for fetching reorder alerts and generating requisitions.
- Implemented FifoCostingService for FIFO cost-layer management and ledger writing.
- Developed StockMutator for applying stock deltas and posting ledger entries.
- Created StockService for stock inquiries and ledger management.
- Implemented TransferService for managing inter-warehouse transfers with dispatch and receive functionalities.

Backend/ERPCore/Program.cs

@@ -6,6 +6,7 @@ using ERPCore.Repositories;
 using ERPCore.Repositories.Interfaces;
 using ERPCore.Services;
 using ERPCore.Services.Interfaces;
+using ERPCore.Services.Stock;
 using ERPCore.System.Errors;
 using Microsoft.EntityFrameworkCore;
 using Microsoft.OpenApi;
@@ -54,6 +55,23 @@ builder.Services.AddScoped<IRequisitionService, RequisitionService>();
 builder.Services.AddScoped<IRfqService, RfqService>();
 builder.Services.AddScoped<IPurchaseOrderService, PurchaseOrderService>();
 
+// Stock core + goods receipt (docs/11 §4–5)
+builder.Services.AddScoped<IFifoCostingService, FifoCostingService>();
+builder.Services.AddScoped<IStockService, StockService>();
+builder.Services.AddScoped<IGrnService, GrnService>();
+
+// Stock transactions + reference data (docs/11 §5–6)
+builder.Services.AddScoped<IStockMutator, StockMutator>();
+builder.Services.AddScoped<IReasonCodeService, ReasonCodeService>();
+builder.Services.AddScoped<IAdjustmentService, AdjustmentService>();
+builder.Services.AddScoped<ITransferService, TransferService>();
+builder.Services.AddScoped<ICountService, CountService>();
+builder.Services.AddScoped<IReorderService, ReorderService>();
+builder.Services.AddScoped<IPurchaseReturnService, PurchaseReturnService>();
+
+// Cross-cutting: audit trail + GL-ready journal read access (docs/11 §6 / FR-X-02, FR-STK-13)
+builder.Services.AddScoped<IAuditService, AuditService>();
+
 // Health checks (EF Core DB)
 builder.Services.AddHealthChecks().AddDbContextCheck<ErpDbContext>();
 
@@ -63,6 +81,13 @@ builder.Services.AddSwaggerGen(o => o.SwaggerDoc("v1", new OpenApiInfo { Title =
 
 var app = builder.Build();
 
+// Seed configurable reference data (reason codes) idempotently at startup.
+using (var scope = app.Services.CreateScope())
+{
+    var db = scope.ServiceProvider.GetRequiredService<ErpDbContext>();
+    await DataSeeder.SeedAsync(db);
+}
+
 app.UseSerilogRequestLogging();
 
 if (app.Environment.IsDevelopment())