feat: material override in new product order wizard (Step 3)

- Dropdown in Step 3 review to set a single material override for all lines
- Override is passed to each OrderLine.material_override at creation time
- Amber background when override is active
- Library materials loaded on Step 3 entry

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/pages/NewProductOrder.tsx

@@ -11,6 +11,8 @@ import { listOutputTypes } from '../api/outputTypes'
 import { createOrder } from '../api/orders'
 import { estimatePrice } from '../api/pricing'
 import { listGlobalRenderPositions } from '../api/renderPositions'
+import { listMaterials } from '../api/materials'
+import type { Material } from '../api/materials'
 import type { Product, RenderPosition } from '../api/products'
 import type { GlobalRenderPosition } from '../api/renderPositions'
 import type { OutputType } from '../api/outputTypes'
@@ -47,6 +49,7 @@ export default function NewProductOrderPage() {
   const [positionSelections, setPositionSelections] = useState<PositionSelections>({})
   const [globalPositionSelections, setGlobalPositionSelections] = useState<GlobalPositionSelections>({})
   const [notes, setNotes] = useState('')
+  const [materialOverride, setMaterialOverride] = useState<string>('')
   const [submitting, setSubmitting] = useState(false)
 
   // ---- Step 1: load products with STEP files ----
@@ -72,6 +75,13 @@ export default function NewProductOrderPage() {
     queryFn: listGlobalRenderPositions,
   })
 
+  const { data: allMaterials } = useQuery({
+    queryKey: ['materials'],
+    queryFn: listMaterials,
+    enabled: step >= 3,
+  })
+  const libMaterials = (allMaterials ?? []).filter((m: Material) => m.schaeffler_code !== null).sort((a: Material, b: Material) => a.name.localeCompare(b.name))
+
   function initPositionsForProduct(product: Product, globals: GlobalRenderPosition[] = []) {
     // Pre-select all per-product positions (if any)
     if ((product.render_positions?.length ?? 0) > 0) {
@@ -378,6 +388,7 @@ export default function NewProductOrderPage() {
           output_type_id: l.outputType.id,
           render_position_id: l.position?.id ?? null,
           global_render_position_id: l.globalPosition?.id ?? null,
+          material_override: materialOverride || null,
         })),
       })
       toast.success(`Draft order ${result.order_number} created — review and submit`)
@@ -823,6 +834,27 @@ export default function NewProductOrderPage() {
                 </table>
               </div>
 
+              {/* Material Override */}
+              <div className="card p-4 mb-4">
+                <label className="block text-sm font-medium text-content-secondary mb-1">
+                  Material Override (optional)
+                </label>
+                <p className="text-xs text-content-muted mb-2">
+                  Apply a single material to all parts of all products in this order. Leave empty to use each product's own materials.
+                </p>
+                <select
+                  value={materialOverride}
+                  onChange={(e) => setMaterialOverride(e.target.value)}
+                  className="w-full max-w-md px-3 py-2 border border-border-default rounded-lg text-sm focus:outline-none focus:border-accent"
+                  style={{ backgroundColor: materialOverride ? 'rgba(245, 158, 11, 0.1)' : 'var(--color-bg-surface)' }}
+                >
+                  <option value="">No material override</option>
+                  {libMaterials.map((m: Material) => (
+                    <option key={m.id} value={m.name}>{m.name}</option>
+                  ))}
+                </select>
+              </div>
+
               {/* Notes */}
               <div className="card p-4 mb-4">
                 <label className="block text-sm font-medium text-content-secondary mb-1">