freifunk: update to accommodate sysinfo changes in ffdd-server.git

hosts/containers/freifunk/configuration.nix

@@ -154,6 +154,7 @@ in {
     timerConfig.OnCalendar = "daily";
   };
 
+  environment.etc."freifunk-server-version".text = "Custom NixOS configuration: 0.0.0";
   # Refresh sysinfo.json
   systemd.services.sysinfo-json = {
     script = ''

hosts/containers/freifunk/sysinfo-json.nix

@@ -56,7 +56,7 @@ stdenv.mkDerivation {
       --replace awk ${gawk}/bin/awk
   '' +
   lib.strings.concatStrings (lib.attrsets.mapAttrsToList (
-    var: value: "substituteInPlace sysinfo-json.cgi --replace ${lib.strings.escapeShellArg "$(nvram get ${var})"} '${value}'\n"
+    var: value: "substituteInPlace sysinfo-json.cgi --replace ${lib.strings.escapeShellArg "$(uci -qX get ffdd.sys.${var})"} '${value}'\n"
   ) nvram);
   installPhase = ''
     pwd