GET /api/v1/statistics/daily-journal?date=YYYY-MM-DD&agent_id=optional

{
  "code": 0,
  "data": {
    "date": "2026-05-31",
    "overview": {
      "total_sessions": 5,
      "total_tokens": 42000,
      "total_cost": 0.35,
      "tool_call_count": 28,
      "approval_count": 2,
      "cron_run_count": 1,
      "kanban_event_count": 3,
      "sessions_by_source": {
        "web": 3,
        "telegram": 1,
        "api": 1
      }
    },
    "sessions": [
      {
        "id": "abc-123",
        "title": "Code review session",
        "source": "web",
        "started_at": "2026-05-31T09:15:00Z",
        "total_tokens": 12000,
        "total_cost": 0.10
      }
    ],
    "approvals": [],
    "cron_runs": [],
    "kanban_events": [],
    "timeline": [
      {
        "type": "session",
        "time": "2026-05-31T09:15:00Z",
        "title": "Code review session",
        "detail": { "source": "web", "tokens": 12000 }
      }
    ]
  }
}