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/JobRepository.cs

@@ -175,4 +175,16 @@ public class JobRepository : Repository<Job>, IJobRepository
             .AsNoTracking()
             .FirstOrDefaultAsync();
     }
+
+    /// <inheritdoc/>
+    public async Task<Job?> LoadForTemplateSnapshotAsync(int jobId)
+    {
+        return await _context.Jobs
+            .Where(j => j.Id == jobId && !j.IsDeleted)
+            .Include(j => j.JobItems.Where(i => !i.IsDeleted))
+                .ThenInclude(i => i.Coats.Where(c => !c.IsDeleted))
+            .Include(j => j.JobItems.Where(i => !i.IsDeleted))
+                .ThenInclude(i => i.PrepServices.Where(p => !p.IsDeleted))
+            .FirstOrDefaultAsync();
+    }
 }