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/InventoryTransactionRepository.cs

@@ -0,0 +1,45 @@
+using Microsoft.EntityFrameworkCore;
+using PowderCoating.Core.Entities;
+using PowderCoating.Core.Enums;
+using PowderCoating.Core.Interfaces.Repositories;
+using PowderCoating.Infrastructure.Data;
+
+namespace PowderCoating.Infrastructure.Repositories;
+
+/// <summary>
+/// Typed repository for <see cref="InventoryTransaction"/> that adds a dynamic-filter
+/// ledger query on top of the generic <see cref="Repository{T}"/>.
+/// </summary>
+public class InventoryTransactionRepository : Repository<InventoryTransaction>, IInventoryTransactionRepository
+{
+    public InventoryTransactionRepository(ApplicationDbContext context) : base(context) { }
+
+    /// <inheritdoc/>
+    public async Task<List<InventoryTransaction>> GetForLedgerAsync(
+        int? itemId,
+        DateTime? from,
+        DateTime? to,
+        InventoryTransactionType? type)
+    {
+        var query = _context.InventoryTransactions
+            .AsNoTracking()
+            .Include(t => t.InventoryItem)
+            .Include(t => t.PurchaseOrder)
+            .Include(t => t.Job)
+            .Where(t => !t.IsDeleted);
+
+        if (itemId.HasValue)
+            query = query.Where(t => t.InventoryItemId == itemId.Value);
+        if (from.HasValue)
+            query = query.Where(t => t.TransactionDate >= from.Value);
+        if (to.HasValue)
+            query = query.Where(t => t.TransactionDate < to.Value.AddDays(1));
+        if (type.HasValue)
+            query = query.Where(t => t.TransactionType == type.Value);
+
+        return await query
+            .OrderByDescending(t => t.TransactionDate)
+            .Take(500)
+            .ToListAsync();
+    }
+}