feat: add boards and tasks management endpoints

backend/app/models/activity_events.py

@@ -0,0 +1,17 @@
+from __future__ import annotations
+
+from datetime import datetime
+from uuid import UUID, uuid4
+
+from sqlmodel import Field, SQLModel
+
+
+class ActivityEvent(SQLModel, table=True):
+    __tablename__ = "activity_events"
+
+    id: UUID = Field(default_factory=uuid4, primary_key=True)
+    event_type: str = Field(index=True)
+    message: str | None = None
+    agent_id: UUID | None = Field(default=None, foreign_key="agents.id", index=True)
+    task_id: UUID | None = Field(default=None, foreign_key="tasks.id", index=True)
+    created_at: datetime = Field(default_factory=datetime.utcnow)