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/parts/registration_submit_part.dart

@@ -34,6 +34,23 @@ extension _RegistrationSubmitPart on _RegistrationPageState {
       }
     }
 
+    // For temp storage target: block if any scanned item is transferred or temp_stored
+    // (on_shelf items are allowed — temp storage acts as shelf change)
+    if (_isTempStorageTarget) {
+      final transferredItems = _findTransferredItemsInScanned();
+      final tempStoredItems = _findTempStoredItemsInScanned();
+      if (transferredItems.isNotEmpty || tempStoredItems.isNotEmpty) {
+        setState(() => _isSubmitting = false);
+        _feedbackService.trigger(FeedbackEvent.submitFailure);
+        _showLocationConflictDialog(
+          onShelfItems: [],
+          transferredItems: transferredItems,
+          tempStoredItems: tempStoredItems,
+        );
+        return;
+      }
+    }
+
     if (_mode == RegistrationMode.multiCode && _zongpaiNos.length > 1) {
       if (_isTransitTarget && !await _ensureBatchSamePaicha(baseUrl)) {
         if (!mounted) return;
@@ -47,7 +64,7 @@ extension _RegistrationSubmitPart on _RegistrationPageState {
         return;
       }
       // Pre-check: block entire batch if any item already has a location binding
-      if (!_isTransitTarget) {
+      if (!_isTransitTarget && !_isTempStorageTarget) {
         final onShelfItems = _findOnShelfItemsInScanned();
         final transferredItems = _findTransferredItemsInScanned();
         if (onShelfItems.isNotEmpty || transferredItems.isNotEmpty) {
@@ -117,13 +134,15 @@ extension _RegistrationSubmitPart on _RegistrationPageState {
       }
       setState(() {
         _zongpaiNos.remove(zongpaiNo);
-        if (_mode == RegistrationMode.singleCode) {
+        if (_mode == RegistrationMode.singleCode && !_isTempStorageTarget) {
           _locationCode = null;
           _locationType = null;
         }
       });
       final msg = result.isOffShelfSuccess
           ? '下架成功'
+          : _isTempStorageTarget
+          ? '变更货架成功'
           : (_mode == RegistrationMode.multiCode ? '多码上架模式，请扫描下一张执行卡' : '上架成功');
       _showStatusOverride(
         msg,