Phases 3 & 4: Complete data access architecture migration

Phase 3 — eliminated ApplicationDbContext from all non-exempt controllers,
routing all data access through IUnitOfWork. Added IPlainRepository<T> for
the four platform entities (Announcement, BannedIp, DashboardTip, ReleaseNote)
that intentionally don't extend BaseEntity and therefore can't use the
constrained IRepository<T>. Added permanent-exception comments to the 18
controllers that legitimately retain direct DbContext access (Identity infra,
cross-tenant platform ops, bulk streaming exports).

Phase 4 — added EnforceDataAccessArchitecture() to Program.cs, a startup
gate that reflects over every Controller subclass and throws at boot if any
non-exempt controller injects ApplicationDbContext. The app cannot start with
a violation.

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

src/PowderCoating.Web/Controllers/SetupWizardController.cs

@@ -8,7 +8,6 @@ using PowderCoating.Application.Services;
 using PowderCoating.Core.Entities;
 using PowderCoating.Core.Enums;
 using PowderCoating.Core.Interfaces;
-using PowderCoating.Infrastructure.Data;
 using PowderCoating.Shared.Constants;
 using System.Text.Json;
 
@@ -20,7 +19,6 @@ public class SetupWizardController : Controller
     private readonly IUnitOfWork _unitOfWork;
     private readonly ITenantContext _tenantContext;
     private readonly UserManager<ApplicationUser> _userManager;
-    private readonly ApplicationDbContext _context;
     private readonly ISeedDataService _seedDataService;
     private readonly ILogger<SetupWizardController> _logger;
 
@@ -28,14 +26,12 @@ public class SetupWizardController : Controller
         IUnitOfWork unitOfWork,
         ITenantContext tenantContext,
         UserManager<ApplicationUser> userManager,
-        ApplicationDbContext context,
         ISeedDataService seedDataService,
         ILogger<SetupWizardController> logger)
     {
         _unitOfWork = unitOfWork;
         _tenantContext = tenantContext;
         _userManager = userManager;
-        _context = context;
         _seedDataService = seedDataService;
         _logger = logger;
     }
@@ -70,14 +66,14 @@ public class SetupWizardController : Controller
         if (company.Preferences == null)
         {
             company.Preferences = new CompanyPreferences { CompanyId = companyId };
-            _context.Set<CompanyPreferences>().Add(company.Preferences);
+            await _unitOfWork.CompanyPreferences.AddAsync(company.Preferences);
             await _unitOfWork.CompleteAsync();
         }
 
         if (company.OperatingCosts == null)
         {
             company.OperatingCosts = new CompanyOperatingCosts { CompanyId = companyId };
-            _context.Set<CompanyOperatingCosts>().Add(company.OperatingCosts);
+            await _unitOfWork.CompanyOperatingCosts.AddAsync(company.OperatingCosts);
             await _unitOfWork.CompleteAsync();
         }