Add CRM features: Outstanding Pickups, Customer Notes, Clone Job, Preferred Powders

- Outstanding Pickups card on Customer Details shows jobs awaiting pickup with age badges
- Customer Notes log: inline add/delete notes with important flag, AJAX-backed
- Clone Job action on Jobs controller; Repeat Last Job button on Customer Details quick actions
- Preferred Powders per customer: typeahead inventory search, AJAX add/remove
- CustomerPreferredPowder entity + migration; unit tests for CRM stats/timeline logic
- Fix EF Core concurrency bug: parallel Task.WhenAll FindAsync replaced with sequential awaits

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

src/PowderCoating.Infrastructure/Repositories/UnitOfWork.cs

@@ -70,6 +70,7 @@ public class UnitOfWork : IUnitOfWork
     private IJobPhotoRepository? _jobPhotos;
     private IRepository<JobNote>? _jobNotes;
     private IRepository<CustomerNote>? _customerNotes;
+    private IRepository<CustomerPreferredPowder>? _customerPreferredPowders;
     private IRepository<JobStatusHistory>? _jobStatusHistory;
     private IRepository<PricingTier>? _pricingTiers;
 
@@ -321,6 +322,8 @@ public class UnitOfWork : IUnitOfWork
     /// <summary>Repository for <see cref="CustomerNote"/> free-text staff notes on customer records; tenant-filtered with soft delete.</summary>
     public IRepository<CustomerNote> CustomerNotes =>
         _customerNotes ??= new Repository<CustomerNote>(_context);
+    public IRepository<CustomerPreferredPowder> CustomerPreferredPowders =>
+        _customerPreferredPowders ??= new Repository<CustomerPreferredPowder>(_context);
 
     /// <summary>Repository for <see cref="JobStatusHistory"/> status-transition audit records; tenant-filtered with soft delete.</summary>
     public IRepository<JobStatusHistory> JobStatusHistory =>