Add AI Quick Quote widget and inline customer reassignment

- New AI Quick Quote floating button: staff type a verbal description to
  get an instant price estimate for phone/walk-in customers; detected
  color names are fuzzy-matched against inventory for stock status;
  saves draft quote under a Walk-In / Phone customer with one click
- Inline customer change on Quote Details and Job Details: always-visible
  native select with inline confirmation banner (no TomSelect dependency);
  ChangeCustomer AJAX endpoints on QuotesController and JobsController
- Quote Edit page: customer dropdown is now editable (lock removed)
- Fix AutoMapper missing CatalogCategory -> UpdateCategoryDto mapping
  that caused a crash on the catalog category Edit page
- Help docs and AI knowledge base updated for all three features

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

src/PowderCoating.Web/Views/Quotes/Edit.cshtml

@@ -23,14 +23,13 @@
         <input type="hidden" asp-for="QuoteStatusId" />
         <partial name="_ValidationSummary" />
 
-        <!-- Section 1: Customer / Prospect/Walk-In (Read-Only) -->
+        <!-- Section 1: Customer / Prospect/Walk-In -->
         <div class="card mb-4">
             <div class="card-header">
                 <h5 class="mb-0"><i class="bi bi-person-circle me-2"></i>Customer / Prospect/Walk-In</h5>
             </div>
             <div class="card-body">
                 <input type="hidden" asp-for="IsForProspect" />
-                <input type="hidden" asp-for="CustomerId" />
 
                 @if (Model.IsForProspect)
                 {
@@ -78,13 +77,13 @@
                 }
                 else
                 {
-                    <!-- Existing Customer (Read-Only Display) -->
-                    <div class="alert alert-light alert-permanent border mb-0 d-flex align-items-center gap-2">
-                        <i class="bi bi-building text-success fs-5"></i>
-                        <div>
-                            <span class="fw-semibold">@ViewBag.CustomerName</span>
-                            <span class="text-muted ms-2 small">Customer cannot be changed after quote creation.</span>
-                        </div>
+                    <!-- Customer Dropdown (now editable) -->
+                    <div class="col-md-6">
+                        <label asp-for="CustomerId" class="form-label fw-semibold">Customer</label>
+                        <select asp-for="CustomerId" asp-items="ViewBag.Customers" id="customerSelect" class="form-select">
+                            <option value="">-- Select Customer --</option>
+                        </select>
+                        <span asp-validation-for="CustomerId" class="text-danger"></span>
                     </div>
                 }
             </div>
@@ -637,6 +636,8 @@
     <script>
         document.addEventListener('DOMContentLoaded', function () {
             initTagInput('quoteTags', 'quoteTagsContainer');
+            var custEl = document.getElementById('customerSelect');
+            if (custEl) new TomSelect(custEl, { placeholder: '-- Select Customer --', openOnFocus: true, maxOptions: false });
         });
 
         // Discount type toggle