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_zh.dart

@@ -537,4 +537,37 @@ class AppLocalizationsZh extends AppLocalizations {
 
   @override
   String get productAddedToShelf => '已添加到储藏室';
+
+  @override
+  String recognitionFoundProducts(int count) {
+    return '找到 $count 个产品';
+  }
+
+  @override
+  String get recognitionAddAll => '全部添加';
+
+  @override
+  String get recognitionAddToStock => '加入储藏室';
+
+  @override
+  String recognitionAdded(int count) {
+    return '已添加 $count 个产品';
+  }
+
+  @override
+  String get recognitionProductsFailed => '添加产品失败';
+
+  @override
+  String get recognitionEmpty => '未找到产品';
+
+  @override
+  String recognitionConfidence(int percent) {
+    return '$percent% 置信度';
+  }
+
+  @override
+  String get recognitionReplaceProduct => '替换产品';
+
+  @override
+  String get scanJobCloseHint => '您可以关闭应用 — 此扫描将显示在产品页面的最近扫描中';
 }