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/DepositsController.cs

@@ -7,7 +7,6 @@ using PowderCoating.Application.DTOs.Company;
 using PowderCoating.Core.Entities;
 using PowderCoating.Core.Enums;
 using PowderCoating.Core.Interfaces;
-using PowderCoating.Infrastructure.Data;
 using PowderCoating.Shared.Constants;
 using QuestPDF.Fluent;
 using QuestPDF.Helpers;
@@ -21,18 +20,15 @@ public class DepositsController : Controller
     private readonly IUnitOfWork _unitOfWork;
     private readonly UserManager<ApplicationUser> _userManager;
     private readonly ILogger<DepositsController> _logger;
-    private readonly ApplicationDbContext _context;
 
     public DepositsController(
         IUnitOfWork unitOfWork,
         UserManager<ApplicationUser> userManager,
-        ILogger<DepositsController> logger,
-        ApplicationDbContext context)
+        ILogger<DepositsController> logger)
     {
         _unitOfWork = unitOfWork;
         _userManager = userManager;
         _logger = logger;
-        _context = context;
     }
 
     // -----------------------------------------------------------------------
@@ -220,11 +216,11 @@ public class DepositsController : Controller
     {
         var prefix = $"DEP-{DateTime.UtcNow:yy}{DateTime.UtcNow.Month:D2}-";
 
-        var existing = await _context.Set<Deposit>()
-            .IgnoreQueryFilters()
-            .Where(d => d.CompanyId == companyId && d.ReceiptNumber.StartsWith(prefix))
+        var existing = (await _unitOfWork.Deposits.FindAsync(
+                d => d.CompanyId == companyId && d.ReceiptNumber.StartsWith(prefix),
+                ignoreQueryFilters: true))
             .Select(d => d.ReceiptNumber)
-            .ToListAsync();
+            .ToList();
 
         var maxNum = 0;
         foreach (var num in existing)