feat: enhance agent heartbeat handling and validate onboarding goal fields

backend/app/schemas/board_onboarding.py

@@ -3,6 +3,7 @@ from __future__ import annotations
 from datetime import datetime
 from uuid import UUID
 
+from pydantic import model_validator
 from sqlmodel import SQLModel
 
 
@@ -21,6 +22,13 @@ class BoardOnboardingConfirm(SQLModel):
     success_metrics: dict[str, object] | None = None
     target_date: datetime | None = None
 
+    @model_validator(mode="after")
+    def validate_goal_fields(self):
+        if self.board_type == "goal":
+            if not self.objective or not self.success_metrics:
+                raise ValueError("Confirmed goal boards require objective and success_metrics")
+        return self
+
 
 class BoardOnboardingRead(SQLModel):
     id: UUID