feat: add temp storage shelf (B prefix) UI support

Recognize B-prefix location codes as temp storage shelves. Add purple
color scheme, conflict detection for temp_stored status, and updated
submit/dialog logic for temp storage target handling.

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

lib/pages/registration/widgets/registration_widgets_part.dart

@@ -5,11 +5,13 @@ part of '../../registration_page.dart';
 extension _RegistrationWidgetsPart on _RegistrationPageState {
   String _locationLabel(CodeType? type) {
     if (type == CodeType.locationTransit) return '转运区域';
+    if (type == CodeType.locationTempStorage) return '暂存货架';
     return '普通货架';
   }
 
   Color _locationLabelColor(CodeType? type) {
     if (type == CodeType.locationTransit) return Colors.orange;
+    if (type == CodeType.locationTempStorage) return const Color(0xFF7B1FA2);
     return Colors.blue;
   }
 
@@ -108,6 +110,12 @@ extension _RegistrationWidgetsPart on _RegistrationPageState {
                       const Color(0xFFE65100),
                       hasData,
                     ),
+                    _buildStatTag(
+                      '暂存 ${stats.tempStoredCount}',
+                      const Color(0xFFF3E5F5),
+                      const Color(0xFF7B1FA2),
+                      hasData,
+                    ),
                   ],
                 ),
               ],
@@ -293,11 +301,13 @@ extension _RegistrationWidgetsPart on _RegistrationPageState {
       status: item.status,
       isScanned: isScanned,
       isTransitTarget: _isTransitTarget,
+      isTempStorageTarget: _isTempStorageTarget,
     );
     final bgColor = registration_calculations.registrationRowBgColor(
       status: item.status,
       isScanned: isScanned,
       isTransitTarget: _isTransitTarget,
+      isTempStorageTarget: _isTempStorageTarget,
     );
 
     return Container(