feat: showDate toggle on card via task modal checkbox

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/prisma/schema.prisma

@@ -52,6 +52,7 @@ model Task {
   issueNote   String?
   startDate   DateTime?
   dueDate     DateTime?
+  showDate    Boolean   @default(true)
   creatorId   String
   assigneeId  String?
   createdAt   DateTime   @default(now())