feat: implement user message redispatching in onboarding process

backend/app/api/board_onboarding.py

@@ -168,6 +168,29 @@ async def start_onboarding(
         .first(session)
     )
     if onboarding:
+        last_user_content: str | None = None
+        messages = onboarding.messages or []
+        if messages:
+            last_message = messages[-1]
+            if isinstance(last_message, dict):
+                last_role = last_message.get("role")
+                content = last_message.get("content")
+                if last_role == "user" and isinstance(content, str) and content:
+                    last_user_content = content
+
+        if last_user_content:
+            # Retrigger the agent when the session is waiting on a response.
+            dispatcher = BoardOnboardingMessagingService(session)
+            await dispatcher.dispatch_answer(
+                board=board,
+                onboarding=onboarding,
+                answer_text=last_user_content,
+                correlation_id=f"onboarding.resume:{board.id}:{onboarding.id}",
+            )
+            onboarding.updated_at = utcnow()
+            session.add(onboarding)
+            await session.commit()
+            await session.refresh(onboarding)
         return onboarding
 
     dispatcher = BoardOnboardingMessagingService(session)