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.Infrastructure/Repositories/JobItemCoatRepository.cs

@@ -0,0 +1,52 @@
+using Microsoft.EntityFrameworkCore;
+using PowderCoating.Core.Entities;
+using PowderCoating.Core.Interfaces.Repositories;
+using PowderCoating.Infrastructure.Data;
+
+namespace PowderCoating.Infrastructure.Repositories;
+
+/// <summary>
+/// Typed repository for <see cref="JobItemCoat"/> that adds ThenInclude-based load methods the
+/// generic <see cref="Repository{T}"/> cannot express.
+/// </summary>
+public class JobItemCoatRepository : Repository<JobItemCoat>, IJobItemCoatRepository
+{
+    public JobItemCoatRepository(ApplicationDbContext context) : base(context) { }
+
+    /// <inheritdoc/>
+    public async Task<JobItemCoat?> LoadForOrderMarkingAsync(int id)
+    {
+        return await _context.JobItemCoats
+            .Include(c => c.JobItem).ThenInclude(i => i.Job).ThenInclude(j => j.Customer)
+            .Include(c => c.Vendor)
+            .Include(c => c.InventoryItem).ThenInclude(i => i!.PrimaryVendor)
+            .FirstOrDefaultAsync(c => c.Id == id);
+    }
+
+    /// <inheritdoc/>
+    public async Task<JobItemCoat?> LoadWithInventoryAsync(int id)
+    {
+        return await _context.JobItemCoats
+            .Include(c => c.InventoryItem)
+            .FirstOrDefaultAsync(c => c.Id == id);
+    }
+
+    /// <inheritdoc/>
+    public async Task<JobItemCoat?> LoadWithJobChainAsync(int id)
+    {
+        return await _context.JobItemCoats
+            .Include(c => c.JobItem).ThenInclude(i => i.Job)
+            .FirstOrDefaultAsync(c => c.Id == id);
+    }
+
+    /// <inheritdoc/>
+    public async Task<List<JobItemCoat>> GetCandidateCoatsForLinkingAsync(int excludeCoatId, int companyId)
+    {
+        return await _context.JobItemCoats
+            .Include(c => c.JobItem)
+            .Where(c => c.Id != excludeCoatId
+                     && c.InventoryItemId == null
+                     && c.JobItem.CompanyId == companyId)
+            .ToListAsync();
+    }
+}