fix: barcode EAN checksum validation + recipe persons dialog conflict

- Manual barcode input now blocks on invalid EAN checksum (was warning-only)
- Native BarcodeDetector now validates EAN/UPC checksum before confirming
- Renamed duplicate adjustRecipePersons (rescaler) to scaleRecipePersons
  to restore +/- buttons in the recipe generation dialog
- Added error.barcode_checksum translation key (all 5 languages)
- Bump version to v1.7.35

manifest.json

@@ -2,7 +2,7 @@
     "name": "EverShelf",
     "short_name": "EverShelf",
     "description": "Gestione completa della dispensa di casa con scansione barcode",
-    "version": "1.7.25",
+    "version": "1.7.35",
     "start_url": "/evershelf/",
     "display": "standalone",
     "background_color": "#f0f4e8",