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/Controllers/QuotesController.cs

@@ -466,6 +466,20 @@ public class QuotesController : Controller
                 .ToListAsync();
             ViewBag.Deposits = quoteDeposits;
 
+            // Customer list for inline customer-change dropdown
+            var allCustomers = await _unitOfWork.Customers.GetAllAsync();
+            ViewBag.CustomerSelectList = allCustomers
+                .Where(c => c.IsActive)
+                .Select(c => new SelectListItem
+                {
+                    Value = c.Id.ToString(),
+                    Text = !string.IsNullOrWhiteSpace(c.CompanyName)
+                        ? c.CompanyName
+                        : $"{c.ContactFirstName} {c.ContactLastName}".Trim()
+                })
+                .OrderBy(c => c.Text)
+                .ToList();
+
             return View(quoteDto);
         }
         catch (Exception ex)
@@ -476,6 +490,40 @@ public class QuotesController : Controller
         }
     }
 
+    /// <summary>
+    /// Reassigns a quote to a different customer. Clears any prospect fields so the
+    /// quote is treated as a real-customer quote after reassignment.
+    /// </summary>
+    [HttpPost]
+    [ValidateAntiForgeryToken]
+    public async Task<IActionResult> ChangeCustomer(int id, int customerId)
+    {
+        var quote = await _unitOfWork.Quotes.GetByIdAsync(id);
+        if (quote == null) return NotFound();
+
+        var customer = await _unitOfWork.Customers.GetByIdAsync(customerId);
+        if (customer == null)
+            return Json(new { success = false, error = "Customer not found." });
+
+        quote.CustomerId = customerId;
+        quote.ProspectCompanyName = null;
+        quote.ProspectContactName = null;
+        quote.ProspectEmail = null;
+        quote.ProspectPhone = null;
+        quote.ProspectAddress = null;
+        quote.ProspectCity = null;
+        quote.ProspectState = null;
+        quote.ProspectZipCode = null;
+
+        await _unitOfWork.CompleteAsync();
+
+        var customerName = !string.IsNullOrWhiteSpace(customer.CompanyName)
+            ? customer.CompanyName
+            : $"{customer.ContactFirstName} {customer.ContactLastName}".Trim();
+
+        return Json(new { success = true, customerName, customerId = customer.Id });
+    }
+
     /// <summary>
     /// Generates and streams the quote PDF.
     /// When <paramref name="inline"/> is true the browser displays it in a viewer tab;
@@ -1299,13 +1347,8 @@ public class QuotesController : Controller
                 return NotFound();
             }
 
-            _logger.LogInformation("Loaded quote {QuoteNumber}, Original CustomerId: {CustomerId}", quote.QuoteNumber, quote.CustomerId);
-
-            // Preserve original customer/prospect assignment (cannot be changed after creation)
-            dto.CustomerId = quote.CustomerId;
-            dto.IsForProspect = !quote.CustomerId.HasValue;
-
-            _logger.LogInformation("After preservation - CustomerId: {CustomerId}, IsForProspect: {IsForProspect}", dto.CustomerId, dto.IsForProspect);
+            // IsForProspect derives from whether a customer was selected in the form
+            dto.IsForProspect = !dto.CustomerId.HasValue;
 
             // Validate at least one quote item exists
             if (dto.QuoteItems == null || dto.QuoteItems.Count == 0)