feat: fully rework 'move list to board' feature to match review requirements

- All async logic for moving lists between boards is now handled via Redux sagas, not in React components.
- Removed direct API calls and sessionStorage usage from UI.
- Added a unified action creator for moving lists between boards.
- Saga watcher now uses the correct action type constant.
- On the backend, the move-to-board helper now:
  - Detaches card members who are not present on the target board.
  - Converts board-wide custom fields to per-card fields when moving lists.
- Added selector memoization in BoardSelectStep to prevent unnecessary rerenders.
- All business logic is now outside of UI components.
- The feature now fully handles:
  - Users (members/assignees) who do not exist on the target board.
  - Board-wide custom fields, which are now either copied or converted to per-card fields.
- All review comments are addressed: no business logic in components, no sessionStorage, all edge cases handled, only sagas and request used for async actions.

server/api/helpers/lists/move-to-board.js

@@ -58,6 +58,57 @@ module.exports = {
     });
     await Promise.all(migrateLabelsPromises);
 
+    await Promise.all(
+      updatedCards.map(async (card) => {
+        const cardMemberships = await CardMembership.find({ cardId: card.id });
+        await Promise.all(
+          cardMemberships.map(async (membership) => {
+            const userMembership = await BoardMembership.findOne({
+              boardId: inputs.targetBoard.id,
+              userId: membership.userId,
+            });
+            if (!userMembership) {
+              await CardMembership.destroy({ id: membership.id });
+            }
+          }),
+        );
+      }),
+    );
+
+    await Promise.all(
+      updatedCards.map(async (card) => {
+        const customFieldValues = await CustomFieldValue.find({ cardId: card.id });
+        await Promise.all(
+          customFieldValues.map(async (value) => {
+            const group = await CustomFieldGroup.findOne({ id: value.customFieldGroupId });
+            if (group && group.boardId && group.boardId !== inputs.targetBoard.id) {
+              const newGroup = await CustomFieldGroup.create({
+                name: group.name,
+                position: group.position,
+                cardId: card.id,
+                baseCustomFieldGroupId: group.baseCustomFieldGroupId,
+              }).fetch();
+              const field = await CustomField.findOne({ id: value.customFieldId });
+              const newField = await CustomField.create({
+                name: field.name,
+                position: field.position,
+                showOnFrontOfCard: field.showOnFrontOfCard,
+                customFieldGroupId: newGroup.id,
+                baseCustomFieldGroupId: field.baseCustomFieldGroupId,
+              }).fetch();
+              await CustomFieldValue.updateOne(
+                { id: value.id },
+                {
+                  customFieldGroupId: newGroup.id,
+                  customFieldId: newField.id,
+                },
+              );
+            }
+          }),
+        );
+      }),
+    );
+
     return {
       updatedList,
       updatedCards,