Add local and NetBox server notes and improve reliability

internal/cache/cache_test.go

@@ -471,3 +471,15 @@ func tempFile(t *testing.T, content []byte) string {
 	f.Close()
 	return f.Name()
 }
+
+func TestUpsertPreservesUsageHistory(t *testing.T) {
+	c := New("", 3600)
+	c.Upsert(Entry{Name: "web01", IP: "10.0.0.1"})
+	c.MarkUsed("web01")
+	before, _ := c.Get("web01")
+	c.Upsert(Entry{Name: "web01", IP: "10.0.0.2"})
+	after, _ := c.Get("web01")
+	if after.LastUsed != before.LastUsed || after.IP != "10.0.0.2" {
+		t.Fatalf("history lost: %+v", after)
+	}
+}