Clean up Nix configuration and remove old files

- Move Nix package and module to nix/ directory for better organization
- Remove old Nix files (systant.nix, systant-old.nix, etc.)
- Remove debug script and systemd service file
- Update config files for new Nix structure
- Add CLAUDE.md with project documentation

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

nix/nixos-module.nix

@@ -0,0 +1,99 @@
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.services.systant;
+in
+{
+  options.services.systant = {
+    enable = mkEnableOption "Systant MQTT Daemon";
+
+    package = mkOption {
+      type = types.package;
+      description = "The systant package to use";
+    };
+
+    mqttHost = mkOption {
+      type = types.str;
+      default = "localhost";
+      description = "MQTT broker hostname";
+    };
+
+    mqttPort = mkOption {
+      type = types.int;
+      default = 1883;
+      description = "MQTT broker port";
+    };
+
+    mqttUsername = mkOption {
+      type = types.nullOr types.str;
+      default = null;
+      description = "MQTT username (null for no auth)";
+    };
+
+    mqttPassword = mkOption {
+      type = types.nullOr types.str;
+      default = null;
+      description = "MQTT password (null for no auth)";
+    };
+
+    statsTopic = mkOption {
+      type = types.str;
+      default = "systant/${config.networking.hostName}/stats";
+      description = "MQTT topic for publishing stats";
+    };
+
+    commandTopic = mkOption {
+      type = types.str;
+      default = "systant/${config.networking.hostName}/commands";
+      description = "MQTT topic for receiving commands";
+    };
+
+    publishInterval = mkOption {
+      type = types.int;
+      default = 30000;
+      description = "Interval between stats publications (milliseconds)";
+    };
+  };
+
+  config = mkIf cfg.enable {
+    systemd.services.systant = {
+      description = "Systant MQTT Daemon";
+      after = [ "network.target" ];
+      wantedBy = [ "multi-user.target" ];
+
+      environment = {
+        SYSTANT_MQTT_HOST = cfg.mqttHost;
+        SYSTANT_MQTT_PORT = toString cfg.mqttPort;
+        SYSTANT_MQTT_USERNAME = mkIf (cfg.mqttUsername != null) cfg.mqttUsername;
+        SYSTANT_MQTT_PASSWORD = mkIf (cfg.mqttPassword != null) cfg.mqttPassword;
+        SYSTANT_STATS_TOPIC = cfg.statsTopic;
+        SYSTANT_COMMAND_TOPIC = cfg.commandTopic;
+        SYSTANT_PUBLISH_INTERVAL = toString cfg.publishInterval;
+        # Override RELEASE_COOKIE to bypass file reading
+        RELEASE_COOKIE = "systant-bypass-cookie";
+      };
+
+      serviceConfig = {
+        Type = "exec";
+        User = "root";
+        Group = "root";
+        ExecStart = "${cfg.package}/bin/systant start";
+        ExecStop = "${cfg.package}/bin/systant stop";
+        Restart = "always";
+        RestartSec = 5;
+        StandardOutput = "journal";
+        StandardError = "journal";
+        SyslogIdentifier = "systant";
+        WorkingDirectory = "${cfg.package}";
+
+        # Security settings
+        NoNewPrivileges = true;
+        PrivateTmp = true;
+        ProtectHome = true;
+        ProtectSystem = false; # Need access to system stats
+      };
+    };
+  };
+}

nix/package.nix

@@ -0,0 +1,32 @@
+{
+  lib,
+  beamPackages,
+  fetchgit,
+}:
+
+beamPackages.mixRelease rec {
+  pname = "systant";
+  version = "0.1.0";
+
+  src = fetchgit {
+    url = "https://git.ryanpandya.com/ryan/systant.git";
+    rev = "54f8d23945bcea17127631a81f8ac318bf7047a6";
+    sha256 = "sha256-1cRfSoH+JdO4a7q4hRZSkoDMk2wMCYRIyCIN56FSUgg=";
+  };
+
+  # Mix dependencies will be automatically fetched and cached by Nix
+  mixFodDeps = beamPackages.fetchMixDeps {
+    pname = "systant-mix-deps";
+    inherit src version;
+    sha256 = "sha256-g8L/ZzCaXznrd+YLCMgvV94NVTKoFnK/Y/RXXPIMAjg=";
+  };
+
+
+  meta = with lib; {
+    description = "Systant - System stats MQTT daemon for monitoring system metrics";
+    homepage = "https://git.ryanpandya.com/ryan/systant";
+    license = licenses.mit;
+    maintainers = [ ];
+    platforms = platforms.linux;
+  };
+}