refactor: round latency graph values to 1 decimal place

Display latency values with single decimal precision (e.g., 114.1ms)
for improved readability in graphs. This ensures consistency between
the raw chart data and tooltip formatting.

lib/towerops_web/live/graph_live/show.ex

@@ -415,7 +415,7 @@ defmodule ToweropsWeb.GraphLive.Show do
   defp latency_check_to_chart_point(check) do
     %{
       x: DateTime.to_unix(check.checked_at, :millisecond),
-      y: check.response_time_ms
+      y: Float.round(check.response_time_ms, 1)
     }
   end