feat: add board goal schemas and validation

backend/app/schemas/approvals.py

@@ -0,0 +1,30 @@
+from __future__ import annotations
+
+from datetime import datetime
+from uuid import UUID
+
+from sqlmodel import SQLModel
+
+
+class ApprovalBase(SQLModel):
+    action_type: str
+    payload: dict[str, object] | None = None
+    confidence: int
+    rubric_scores: dict[str, int] | None = None
+    status: str = "pending"
+
+
+class ApprovalCreate(ApprovalBase):
+    agent_id: UUID | None = None
+
+
+class ApprovalUpdate(SQLModel):
+    status: str | None = None
+
+
+class ApprovalRead(ApprovalBase):
+    id: UUID
+    board_id: UUID
+    agent_id: UUID | None = None
+    created_at: datetime
+    resolved_at: datetime | None = None