feat: localise scan screen (12 languages)

Replace all hardcoded Russian strings in ScanScreen and _LoadingDialog
with AppLocalizations keys; add addFromReceiptOrPhoto, chooseMethod,
photoReceipt, photoReceiptSubtitle, photoProducts, photoProductsSubtitle,
recognizing keys to all 12 ARB files and regenerate AppLocalizations.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/lib/l10n/app_ar.arb

@@ -96,5 +96,11 @@
   "mealTypeSnack": "وجبة خفيفة",
   "navHome": "الرئيسية",
   "navProducts": "المنتجات",
-  "navRecipes": "الوصفات"
+  "navRecipes": "الوصفات",
+  "addFromReceiptOrPhoto": "إضافة من الإيصال أو الصورة",
+  "chooseMethod": "اختر الطريقة",
+  "photoReceipt": "تصوير الإيصال",
+  "photoReceiptSubtitle": "التعرف على جميع المنتجات من الإيصال",
+  "photoProducts": "تصوير المنتجات",
+  "photoProductsSubtitle": "الثلاجة، الطاولة، الرف — حتى 3 صور"
 }