feat: improved receipt recognition, batch product add, and scan UX

- Rewrite receipt OCR prompt: completes truncated names, preserves fat%
  and flavour attributes, extracts weight/volume from line, infers
  typical package sizes for solid goods with quantity_confidence field
- Add quantity_confidence to RecognizedItem, EnrichedItem, and
  ProductJobResultItem; propagate through item enricher and worker
- Replace per-item create loop with single POST /user-products/batch call
  from RecognitionConfirmScreen
- Rebuild RecognitionConfirmScreen: amber qty border for low
  quantity_confidence, tappable product name → catalog picker,
  sort items by confidence, full L10n (no hardcoded strings)
- Add timestamps (HH:mm / d MMM HH:mm) to recent scan chips
- Show close-app hint on ProductJobWatchScreen (queued + processing)
- Refresh recentProductJobsProvider on watch screen init so new job
  appears without a manual pull-to-refresh
- App-level WidgetsBindingObserver refreshes product and dish job lists
  on resume, fixing stale lists after background/foreground transitions
- Add 9 new L10n keys across all 12 locales

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

client/lib/l10n/app_localizations_ja.dart

@@ -538,4 +538,37 @@ class AppLocalizationsJa extends AppLocalizations {
 
   @override
   String get productAddedToShelf => 'パントリーに追加しました';
+
+  @override
+  String recognitionFoundProducts(int count) {
+    return '$count個の商品が見つかりました';
+  }
+
+  @override
+  String get recognitionAddAll => 'すべて追加';
+
+  @override
+  String get recognitionAddToStock => 'パントリーに追加';
+
+  @override
+  String recognitionAdded(int count) {
+    return '$count個の商品を追加しました';
+  }
+
+  @override
+  String get recognitionProductsFailed => '商品の追加に失敗しました';
+
+  @override
+  String get recognitionEmpty => '商品が見つかりません';
+
+  @override
+  String recognitionConfidence(int percent) {
+    return '$percent%の信頼度';
+  }
+
+  @override
+  String get recognitionReplaceProduct => '商品を置き換える';
+
+  @override
+  String get scanJobCloseHint => 'アプリを閉じても大丈夫です — このスキャンは製品画面の最近のスキャンに表示されます';
 }