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.Core/Interfaces/IUnitOfWork.cs

@@ -1,4 +1,5 @@
 using PowderCoating.Core.Entities;
+using PowderCoating.Core.Interfaces.Repositories;
 
 namespace PowderCoating.Core.Interfaces;
 
@@ -15,14 +16,14 @@ public interface IUnitOfWork : IDisposable
     // Powder Insights
     IRepository<PowderUsageLog> PowderUsageLogs { get; }
 
-    // Core entities
-    IRepository<Customer> Customers { get; }
-    IRepository<Job> Jobs { get; }
+    // Core entities — typed repositories for complex domains
+    ICustomerRepository Customers { get; }
+    IJobRepository Jobs { get; }
     IRepository<JobDailyPriority> JobDailyPriorities { get; }
     IRepository<JobItem> JobItems { get; }
     IRepository<JobItemCoat> JobItemCoats { get; }
     IRepository<JobChangeHistory> JobChangeHistories { get; }
-    IRepository<Quote> Quotes { get; }
+    IQuoteRepository Quotes { get; }
     IRepository<QuotePhoto> QuotePhotos { get; }
     IRepository<QuoteItem> QuoteItems { get; }
     IRepository<QuoteItemCoat> QuoteItemCoats { get; }
@@ -69,19 +70,19 @@ public interface IUnitOfWork : IDisposable
     IRepository<OvenBatch> OvenBatches { get; }
     IRepository<OvenBatchItem> OvenBatchItems { get; }
 
-    // Invoices, Payments & Deposits
-    IRepository<Invoice> Invoices { get; }
+    // Invoices, Payments & Deposits — typed repository for complex include chains
+    IInvoiceRepository Invoices { get; }
     IRepository<InvoiceItem> InvoiceItems { get; }
     IRepository<Payment> Payments { get; }
     IRepository<Deposit> Deposits { get; }
 
-    // Purchase Orders
-    IRepository<PurchaseOrder> PurchaseOrders { get; }
+    // Purchase Orders — typed repository for paged/filtered list and detail load
+    IPurchaseOrderRepository PurchaseOrders { get; }
     IRepository<PurchaseOrderItem> PurchaseOrderItems { get; }
 
-    // Expense Tracking / Accounts Payable
+    // Expense Tracking / Accounts Payable — typed repository for Bills
     IRepository<Account> Accounts { get; }
-    IRepository<Bill> Bills { get; }
+    IBillRepository Bills { get; }
     IRepository<BillLineItem> BillLineItems { get; }
     IRepository<BillPayment> BillPayments { get; }
     IRepository<Expense> Expenses { get; }