fix: next follow up date should be always greater then current time (#24308)

diff --git a/erpnext/crm/doctype/opportunity/opportunity.js b/erpnext/crm/doctype/opportunity/opportunity.js
index 08958b7..ac374a9 100644
--- a/erpnext/crm/doctype/opportunity/opportunity.js
+++ b/erpnext/crm/doctype/opportunity/opportunity.js
@@ -24,6 +24,12 @@
 			frm.trigger('set_contact_link');
 		}
 	},
+	contact_date: function(frm) {
+		if(frm.doc.contact_date < frappe.datetime.now_datetime()){
+			frm.set_value("contact_date", "");
+			frappe.throw(__("Next follow up date should be greater than now."))
+		}
+	},
 
 	onload_post_render: function(frm) {
 		frm.get_field("items").grid.set_multiple_add("item_code", "qty");