feat: add boards and tasks management endpoints

backend/app/schemas/activity_events.py

@@ -0,0 +1,15 @@
+from __future__ import annotations
+
+from datetime import datetime
+from uuid import UUID
+
+from sqlmodel import SQLModel
+
+
+class ActivityEventRead(SQLModel):
+    id: UUID
+    event_type: str
+    message: str | None
+    agent_id: UUID | None
+    task_id: UUID | None
+    created_at: datetime