feat: add kernel version reporting for all platforms

monitoring/unit/os_freebsd.go

@@ -19,3 +19,14 @@ func OSName() string {
 	name := strings.TrimSpace(string(output))
 	return name
 }
+
+// KernelVersion returns the kernel version on FreeBSD
+func KernelVersion() string {
+	cmd := exec.Command("uname", "-r")
+	output, err := cmd.Output()
+	if err != nil {
+		return "Unknown"
+	}
+
+	return strings.TrimSpace(string(output))
+}