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_localizations_ko.dart

@@ -285,4 +285,22 @@ class AppLocalizationsKo extends AppLocalizations {
 
   @override
   String get navRecipes => '레시피';
+
+  @override
+  String get addFromReceiptOrPhoto => '영수증 또는 사진으로 추가';
+
+  @override
+  String get chooseMethod => '방법 선택';
+
+  @override
+  String get photoReceipt => '영수증 촬영';
+
+  @override
+  String get photoReceiptSubtitle => '영수증의 모든 상품 인식';
+
+  @override
+  String get photoProducts => '식품 촬영';
+
+  @override
+  String get photoProductsSubtitle => '냉장고, 테이블, 선반 — 최대 3장';
 }