Add customer approval status messages and admin delete option

Customer-facing changes:
- Show approval status message when design is submitted
- Display pending approval notification with email confirmation
- Show approved confirmation when design is ready
- Show rejection message for designs needing changes

Admin-facing changes:
- Add delete button to design approval detail page
- Confirmation dialog before deletion
- Proper cleanup of design and associated messages
- Redirect to designs list after deletion

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

src/app/admin/designs/[id]/page.tsx

@@ -1,6 +1,7 @@
 'use client';
 
 import { useState, useEffect } from 'react';
+import { useRouter } from 'next/navigation';
 import Link from 'next/link';
 import DesignApprovalChat from '@/components/DesignApprovalChat';
 import AdminDesignEditor from '@/components/AdminDesignEditor';
@@ -28,9 +29,11 @@ interface DesignApproval {
 }
 
 export default function DesignDetailPage({ params }: { params: { id: string } }) {
+  const router = useRouter();
   const [design, setDesign] = useState<DesignApproval | null>(null);
   const [loading, setLoading] = useState(true);
   const [approving, setApproving] = useState(false);
+  const [deleting, setDeleting] = useState(false);
   const [editingDesign, setEditingDesign] = useState(false);
 
   useEffect(() => {
@@ -56,6 +59,22 @@ export default function DesignDetailPage({ params }: { params: { id: string } })
     }
   };
 
+  const handleDelete = async () => {
+    if (!confirm('Are you sure you want to delete this design? This cannot be undone.')) return;
+
+    setDeleting(true);
+    try {
+      const res = await fetch(`/api/designs/${params.id}`, { method: 'DELETE' });
+      if (res.ok) {
+        router.push('/admin/designs');
+      } else {
+        alert('Failed to delete design');
+      }
+    } finally {
+      setDeleting(false);
+    }
+  };
+
   const handleEditorSave = (designJson: string, previewUrl: string) => {
     setDesign((prev) =>
       prev
@@ -202,6 +221,15 @@ export default function DesignDetailPage({ params }: { params: { id: string } })
                 </button>
               </div>
             )}
+            <div className="mt-4 pt-4 border-t border-line">
+              <button
+                onClick={handleDelete}
+                disabled={deleting}
+                className="w-full bg-red-600 px-4 py-2 text-sm font-medium text-paper hover:bg-red-700 disabled:opacity-60"
+              >
+                {deleting ? 'Deleting…' : 'Delete Design'}
+              </button>
+            </div>
           </div>
 
           {/* Chat */}