Add reference size fields to product admin editor

- Add referenceWidthCm and referenceHeightCm to ProductDTO
- Update toProductDTO to include reference size fields
- Add reference size inputs to admin product edit page
- Update updateProduct action to handle reference sizes
- Rulers on personalization page use product reference size

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/app/admin/products/[id]/edit/page.tsx

@@ -285,6 +285,41 @@ export default async function EditProductPage({ params }: { params: { id: string
           </label>
         </div>
 
+        <div className="grid grid-cols-2 gap-4">
+          <div>
+            <label htmlFor="referenceWidthCm" className="tag-label mb-2 block">
+              Reference width (cm)
+            </label>
+            <input
+              id="referenceWidthCm"
+              name="referenceWidthCm"
+              type="number"
+              step="0.1"
+              min="0"
+              placeholder="e.g. 40"
+              defaultValue={product.referenceWidthCm ?? ''}
+              className="w-full border border-line bg-paper px-3 py-2 text-sm"
+            />
+            <p className="mt-1 text-xs text-muted">Width of garment/object for ruler reference (optional)</p>
+          </div>
+          <div>
+            <label htmlFor="referenceHeightCm" className="tag-label mb-2 block">
+              Reference height (cm)
+            </label>
+            <input
+              id="referenceHeightCm"
+              name="referenceHeightCm"
+              type="number"
+              step="0.1"
+              min="0"
+              placeholder="e.g. 60"
+              defaultValue={product.referenceHeightCm ?? ''}
+              className="w-full border border-line bg-paper px-3 py-2 text-sm"
+            />
+            <p className="mt-1 text-xs text-muted">Height of garment/object for ruler reference (optional)</p>
+          </div>
+        </div>
+
         <div>
           <label className="tag-label mb-2 block">Colors</label>
           <ColorPicker

src/app/admin/products/actions.ts

@@ -168,6 +168,10 @@ export async function updateProduct(formData: FormData) {
   const showOnPersonalised = String(formData.get('showOnPersonalised') ?? '') === '1';
   const showOnProducts = String(formData.get('showOnProducts') ?? '') === '1';
   const collectionIds = formData.getAll('collections').map((v) => String(v));
+  const referenceWidthCmInput = String(formData.get('referenceWidthCm') ?? '').trim();
+  const referenceHeightCmInput = String(formData.get('referenceHeightCm') ?? '').trim();
+  const referenceWidthCm = referenceWidthCmInput ? Number(referenceWidthCmInput) : null;
+  const referenceHeightCm = referenceHeightCmInput ? Number(referenceHeightCmInput) : null;
 
   if (!id) throw new Error('Missing product id.');
   if (!name || !category || !priceDollars) {
@@ -228,6 +232,8 @@ export async function updateProduct(formData: FormData) {
     photoRecolorable: boolean;
     showOnPersonalised: boolean;
     showOnProducts: boolean;
+    referenceWidthCm: number | null;
+    referenceHeightCm: number | null;
     imageUrl?: string;
     imageUrlBack?: string;
     printArea?: string;
@@ -247,6 +253,8 @@ export async function updateProduct(formData: FormData) {
     photoRecolorable,
     showOnPersonalised,
     showOnProducts,
+    referenceWidthCm,
+    referenceHeightCm,
   };
 
   // Only touch the front photo/print area if a new photo was actually uploaded —