Fix catalog item pricing and rogue margin-points text

Catalog DefaultPrice is always the base price — removed the IncludePrepCost
gate that was adding prep service labor on top of catalog items. PrepServices
on catalog items exist for scheduling purposes only, not pricing.

Also fixed Razor syntax bug in Details.cshtml where @(expr).ToString("F1")
rendered the raw decimal followed by the literal string ".ToString("F1")"
instead of the formatted value.

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

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

@@ -1230,7 +1230,7 @@
                                         var priceBeforeDiscount = pb.Total + pb.DiscountAmount;
                                         var marginBeforeDiscount = priceBeforeDiscount > 0 ? ((priceBeforeDiscount - totalDirectCost) / priceBeforeDiscount * 100m) : 0m;
                                         <div class="small text-muted">
-                                            Without discount: @marginBeforeDiscount.ToString("F1")% — discount cost you @(marginBeforeDiscount - effectiveMargin).ToString("F1") margin points
+                                            Without discount: @marginBeforeDiscount.ToString("F1")% — discount cost you @((marginBeforeDiscount - effectiveMargin).ToString("F1")) margin points
                                         </div>
                                     }
                                 }