fix: add photo_path fields to frontend Item interface to display saved photos

The backend returns photo_path, photo_thumbnail_path, and photo_upload_date
from the AI auto-save feature, but the frontend Item interface was missing
these fields, causing images not to display in ItemDetailModal and InventoryTable.

Updated:
- frontend/lib/db.ts: Added missing photo fields to Item interface
- frontend/components/ItemDetailModal.tsx: Use photo_path first, fallback to image_url
- frontend/components/InventoryTable.tsx: Use photo_path first, fallback to image_url

This ensures the UI can now display photos saved by the auto-photo-save feature.

frontend/lib/db.ts

@@ -19,6 +19,9 @@ export interface Item {
   connector?: string;
   size?: string;
   ocr_text?: string;
+  photo_path?: string;
+  photo_thumbnail_path?: string;
+  photo_upload_date?: string;
 }
 
 export interface PendingOperation {