Reverted New UI Design of WeKan v8.29 and added more fixes and performance improvements.

Thanks to xet7 !

server/attachmentMigrationStatus.js

@@ -0,0 +1,22 @@
+import { Mongo } from 'meteor/mongo';
+
+// Server-side collection for attachment migration status
+export const AttachmentMigrationStatus = new Mongo.Collection('attachmentMigrationStatus');
+
+// Allow/Deny rules
+// This collection is server-only and should not be modified by clients
+// Allow server-side operations (when userId is undefined) but deny all client operations
+if (Meteor.isServer) {
+  AttachmentMigrationStatus.allow({
+    insert: (userId) => !userId,
+    update: (userId) => !userId,
+    remove: (userId) => !userId,
+  });
+}
+
+// Create indexes for better query performance
+Meteor.startup(() => {
+  AttachmentMigrationStatus._collection.createIndexAsync({ boardId: 1 });
+  AttachmentMigrationStatus._collection.createIndexAsync({ userId: 1, boardId: 1 });
+  AttachmentMigrationStatus._collection.createIndexAsync({ updatedAt: -1 });
+});