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_ja.dart

@@ -285,4 +285,22 @@ class AppLocalizationsJa extends AppLocalizations {
 
   @override
   String get navRecipes => 'レシピ';
+
+  @override
+  String get addFromReceiptOrPhoto => 'レシートや写真から追加';
+
+  @override
+  String get chooseMethod => '方法を選択';
+
+  @override
+  String get photoReceipt => 'レシートを撮影';
+
+  @override
+  String get photoReceiptSubtitle => 'レシートから全商品を認識';
+
+  @override
+  String get photoProducts => '食品を撮影';
+
+  @override
+  String get photoProductsSubtitle => '冷蔵庫・テーブル・棚 — 最大3枚';
 }