feat(core): Add support for WebSockets as an alternative to Server-Sent Events (#5443)

Co-authored-by: Matthijs Knigge <matthijs@volcano.nl>

packages/cli/src/config/schema.ts

@@ -925,6 +925,15 @@ export const schema = {
 		},
 	},
 
+	push: {
+		backend: {
+			format: ['sse', 'websocket'] as const,
+			default: 'sse',
+			env: 'N8N_PUSH_BACKEND',
+			doc: 'Backend to use for push notifications',
+		},
+	},
+
 	binaryDataManager: {
 		availableModes: {
 			format: String,