Function handle_status 

pub async fn handle_status(
    req: HttpRequest,
    state: Data<AppState>,
) -> Result<HttpResponse, HaystackError>

GET /api/system/status

Returns a single-row grid with server status information:

• uptime: seconds since the server started (with “s” unit)
• entityCount: number of entities in the graph
• watchCount: number of active watch subscriptions