fix: use correct nested biz node structure for interactive messages

Changes the biz node from flat structure (biz > native_flow) to nested
structure (biz > interactive > native_flow) as used by Pastorini/Astra-Api.

Structure:
- biz: {}
  - interactive: { type: 'native_flow', v: '1' }
    - native_flow: { v: '9', name: 'mixed' }

This fixes error 479 that was breaking all interactive messages.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/Socket/messages-send.ts

@@ -1137,13 +1137,27 @@ export const makeMessagesSocket = (config: SocketConfig) => {
 				metrics.interactiveMessagesSent.inc({ type: buttonType })
 
 				try {
+					// Use nested structure: biz > interactive > native_flow
+					// This matches the working Pastorini/Astra-Api implementation
 					;(stanza.content as BinaryNode[]).push({
 						tag: 'biz',
 						attrs: {},
 						content: [
 							{
-								tag: buttonType,
-								attrs: getButtonArgs(message)
+								tag: 'interactive',
+								attrs: {
+									type: 'native_flow',
+									v: '1'
+								},
+								content: [
+									{
+										tag: 'native_flow',
+										attrs: {
+											v: '9',
+											name: 'mixed'
+										}
+									}
+								]
 							}
 						]
 					})