Add global live feed for task comments

backend/app/schemas/activity_events.py

@@ -13,3 +13,16 @@ class ActivityEventRead(SQLModel):
     agent_id: UUID | None
     task_id: UUID | None
     created_at: datetime
+
+
+class ActivityTaskCommentFeedItemRead(SQLModel):
+    id: UUID
+    created_at: datetime
+    message: str | None
+    agent_id: UUID | None
+    agent_name: str | None = None
+    agent_role: str | None = None
+    task_id: UUID
+    task_title: str
+    board_id: UUID
+    board_name: str