fix: show item save confirmation with image before closing

- Add savingIndex state to track saving operation
- Display success overlay with saved image for 1.5 seconds
- Show item name in confirmation message
- Prevents modal from closing immediately after save

Fixes user complaint about image disappearing too quickly without confirmation

frontend/components/AIOnboarding.tsx

@@ -29,6 +29,7 @@ export default function AIOnboarding({ onCancel, onComplete, categories, invento
     fileInputRef,
     existingTypes,
     existingBoxes,
+    savingIndex,
     startLiveCamera,
     stopLiveCamera,
     captureSnapshot,
@@ -483,6 +484,27 @@ export default function AIOnboarding({ onCancel, onComplete, categories, invento
           </div>
         </div>
       )}
+
+      {/* Success confirmation overlay */}
+      {savingIndex !== null && image && (
+        <div className="fixed inset-0 bg-black/70 flex items-center justify-center z-50 animate-in fade-in duration-200">
+          <div className="flex flex-col items-center gap-4">
+            <div className="w-48 h-48 rounded-3xl overflow-hidden border-4 border-green-500 shadow-2xl">
+              <img
+                src={image}
+                alt="Saved item photo"
+                className="w-full h-full object-contain bg-black"
+              />
+            </div>
+            <div className="text-center">
+              <p className="text-white text-lg font-normal mb-2">Item saved!</p>
+              <p className="text-secondary text-xs font-normal">
+                {extractedItems[savingIndex]?.Item || extractedItems[savingIndex]?.name || "New item"} added to catalog
+              </p>
+            </div>
+          </div>
+        </div>
+      )}
     </div>
   );
 }