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.Web/Views/Jobs/Details.cshtml

@@ -19,6 +19,10 @@
                         title="Save this job as a reusable template">
                     <i class="bi bi-layout-text-window-reverse me-2"></i>Save as Template
                 </button>
+                <a asp-action="CloneJob" asp-route-id="@Model.Id" class="btn btn-outline-secondary"
+                   title="Create a new job pre-filled with this job&apos;s items and settings">
+                    <i class="bi bi-arrow-repeat me-2"></i>Clone Job
+                </a>
                 <a asp-action="Edit" asp-route-id="@Model.Id" class="btn btn-warning">
                     <i class="bi bi-pencil me-2"></i>Edit
                 </a>