Phase 1: Introduce typed repository interfaces and report service stubs

Six IUnitOfWork properties upgraded from generic IRepository<T> to domain-specific
typed interfaces (IJobRepository, IQuoteRepository, IInvoiceRepository,
ICustomerRepository, IBillRepository, IPurchaseOrderRepository). Each backed by a
concrete typed repository that encapsulates complex include chains previously
inlined in controllers.

Also adds IFinancialReportService and IOperationalReportService stub implementations
(NotImplementedException placeholders) to Application.Interfaces and Infrastructure.Services,
registered in Program.cs. These are the migration targets for ReportsController's
aggregate query methods in Phase 2.

No controller behaviour changed in this commit — all callers still compile because
typed interfaces extend IRepository<T>.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/PowderCoating.Web/Program.cs

@@ -199,6 +199,8 @@ builder.Services.AddScoped<IAiQuickQuoteService, AiQuickQuoteService>();
 builder.Services.AddSingleton<IAiUsageLogger, AiUsageLogger>();
 builder.Services.AddScoped<IAiSchedulingService, AiSchedulingService>();
 builder.Services.AddScoped<IAccountingAiService, AccountingAiService>();
+builder.Services.AddScoped<IFinancialReportService, FinancialReportService>();
+builder.Services.AddScoped<IOperationalReportService, OperationalReportService>();
 builder.Services.AddScoped<IAiHelpService, AiHelpService>();
 builder.Services.AddScoped<IAiCatalogPriceCheckService, AiCatalogPriceCheckService>();
 builder.Services.AddScoped<IInventoryAiLookupService, InventoryAiLookupService>();