Add download photo button to custom request detail page

- Create DownloadPhotoButton component for downloading customer photos
- Add download button before 'Start a design for this' button
- Allows admin to save photo locally for editing in design software before approval

Addresses user request: admin should be able to download photo from request
for editing before uploading final design to the approval flow.

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

src/app/admin/custom-requests/[id]/page.tsx

@@ -3,6 +3,7 @@ import { notFound } from 'next/navigation';
 import { prisma } from '@/lib/prisma';
 import AdminNav from '@/components/AdminNav';
 import ShareButtons from '@/components/ShareButtons';
+import DownloadPhotoButton from '@/components/DownloadPhotoButton';
 import { deleteRequest, markRequestDone, markRequestNew } from '../actions';
 
 export default async function CustomRequestDetailPage({ params }: { params: { id: string } }) {
@@ -59,6 +60,8 @@ export default async function CustomRequestDetailPage({ params }: { params: { id
       </div>
 
       <div className="mt-8 flex flex-wrap gap-3">
+        <DownloadPhotoButton photoUrl={request.imageDataUrl} customerName={request.customerName} />
+
         <Link
           href={`/admin/proofs/new?${newProofParams.toString()}`}
           className="bg-clay px-6 py-3 text-sm font-medium text-paper hover:bg-clay-dark"