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/dialogs/registration_dialogs_part.dart

@@ -97,6 +97,7 @@ extension _RegistrationDialogsPart on _RegistrationPageState {
   void _showLocationConflictDialog({
     required List<PaichaOverviewItem> onShelfItems,
     required List<PaichaOverviewItem> transferredItems,
+    List<PaichaOverviewItem> tempStoredItems = const [],
   }) {
     final contentParts = <Widget>[];
 
@@ -142,6 +143,29 @@ extension _RegistrationDialogsPart on _RegistrationPageState {
       }
     }
 
+    if (tempStoredItems.isNotEmpty) {
+      if (onShelfItems.isNotEmpty || transferredItems.isNotEmpty) {
+        contentParts.add(const Divider());
+        contentParts.add(const SizedBox(height: 4));
+      }
+      contentParts.add(
+        Text(
+          '暂存中',
+          style: TextStyle(
+            fontWeight: FontWeight.bold,
+            color: const Color(0xFF7B1FA2),
+          ),
+        ),
+      );
+      for (final item in tempStoredItems) {
+        contentParts.addAll([
+          Text('总排号：${item.zongpaiNo}'),
+          Text('暂存货位：${item.locationCode ?? "未知"}'),
+          const SizedBox(height: 6),
+        ]);
+      }
+    }
+
     contentParts.add(const SizedBox(height: 4));
     contentParts.add(
       const Text(