feat: allow on_shelf items in transit batch transfer

Transit shelf registration is effectively an off-shelf operation. Allow
not_shelved, on_shelf, and their mix when target is a transit shelf.
Only transferred items are blocked since they are already in transit.

Also fix conflict color logic: transferred items now correctly show as
red (conflict) for both transit and normal shelf targets.

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

lib/pages/registration/parts/registration_submit_part.dart

@@ -19,15 +19,15 @@ extension _RegistrationSubmitPart on _RegistrationPageState {
 
     setState(() => _isSubmitting = true);
 
-    // For transit target: block if any scanned item already has a location
+    // For transit target: block if any scanned item is already transferred
+    // (on_shelf items are allowed — transit registration acts as off-shelf)
     if (_isTransitTarget) {
-      if (_hasAnyLocatedInScanned()) {
+      final transferredItems = _findTransferredItemsInScanned();
-        final onShelfItems = _findOnShelfItemsInScanned();
+      if (transferredItems.isNotEmpty) {
-        final transferredItems = _findTransferredItemsInScanned();
         setState(() => _isSubmitting = false);
         _feedbackService.trigger(FeedbackEvent.submitFailure);
         _showLocationConflictDialog(
-          onShelfItems: onShelfItems,
+          onShelfItems: [],
           transferredItems: transferredItems,
         );
         return;

lib/pages/registration/registration_calculations.dart

@@ -110,9 +110,10 @@ Color registrationBarColor({
   required bool isTransitTarget,
 }) {
   if (isScanned) {
-    return status == 'on_shelf' && !isTransitTarget
+    final isConflict = isTransitTarget
-        ? Colors.red
+        ? status == 'transferred'
-        : const Color(0xFF43A047);
+        : (status == 'on_shelf' || status == 'transferred');
+    return isConflict ? Colors.red : const Color(0xFF43A047);
   }
 
   switch (status) {
@@ -131,9 +132,10 @@ Color registrationRowBgColor({
   required bool isTransitTarget,
 }) {
   if (isScanned) {
-    return status == 'on_shelf' && !isTransitTarget
+    final isConflict = isTransitTarget
-        ? Colors.red.shade50
+        ? status == 'transferred'
-        : const Color(0xFFF1F8E9);
+        : (status == 'on_shelf' || status == 'transferred');
+    return isConflict ? Colors.red.shade50 : const Color(0xFFF1F8E9);
   }
 
   switch (status) {