feat(server): retention GenServer prunes samples older than 48h hourly

server/test/server/retention_test.exs

@@ -0,0 +1,21 @@
+defmodule Server.RetentionTest do
+  use Server.DataCase, async: false
+
+  alias Server.{Hosts, Metrics, Retention}
+
+  test "prune_now/1 deletes samples older than the retention window" do
+    {:ok, {host, _}} = Hosts.create_host("pve-01")
+    stale_at = DateTime.add(DateTime.utc_now(), -49 * 3600, :second)
+    fresh_at = DateTime.add(DateTime.utc_now(), -60, :second)
+
+    {:ok, _} = Metrics.record_sample(host.id, "fast", stale_at, %{"x" => 1})
+    {:ok, fresh} = Metrics.record_sample(host.id, "fast", fresh_at, %{"x" => 2})
+
+    {deleted, _} = Retention.prune_now(48 * 3600)
+
+    assert deleted == 1
+    remaining = Server.Repo.all(Server.Schema.Metric)
+    assert length(remaining) == 1
+    assert hd(remaining).id == fresh.id
+  end
+end