feat(nixos): add navidrome guest module

configs/nixos/modules/services/navidrome.nix

@@ -0,0 +1,92 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+let
+  cfg = config.modules.services.navidrome;
+in
+{
+  options.modules.services.navidrome = {
+    enable = lib.mkEnableOption "Navidrome";
+
+    package = lib.mkPackageOption pkgs "navidrome" { };
+
+    port = lib.mkOption {
+      type = lib.types.port;
+      default = 4533;
+      description = "Port Navidrome listens on.";
+    };
+
+    dataDir = lib.mkOption {
+      type = lib.types.str;
+      default = "/var/lib/navidrome";
+      description = "Directory where Navidrome stores state.";
+    };
+
+    musicDir = lib.mkOption {
+      type = lib.types.str;
+      default = "/music";
+      description = "Directory where Navidrome reads the music library.";
+    };
+
+    user = lib.mkOption {
+      type = lib.types.str;
+      default = "navidrome";
+      description = "User account that runs Navidrome.";
+    };
+
+    group = lib.mkOption {
+      type = lib.types.str;
+      default = "storage";
+      description = "Group account that owns Navidrome state and media access.";
+    };
+
+    enableSharing = lib.mkOption {
+      type = lib.types.bool;
+      default = true;
+      description = "Enables Navidrome sharing support.";
+    };
+
+    settings = lib.mkOption {
+      type = lib.types.attrs;
+      default = { };
+      description = "Additional non-secret Navidrome settings.";
+    };
+
+    environmentFile = lib.mkOption {
+      type = lib.types.nullOr lib.types.path;
+      default = null;
+      description = "File containing secret Navidrome environment variables.";
+    };
+  };
+
+  config = lib.mkMerge [
+    {
+      registry."stable-uid".${config.networking.hostName}.navidrome = 20004;
+    }
+
+    (lib.mkIf cfg.enable {
+      users.users.${cfg.user} = {
+        isSystemUser = true;
+        uid = config.registry."stable-uid".${config.networking.hostName}.navidrome;
+        group = cfg.group;
+        home = cfg.dataDir;
+      };
+
+      services.navidrome = {
+        enable = true;
+        inherit (cfg) package user group environmentFile;
+        openFirewall = true;
+        settings = cfg.settings // {
+          Address = "0.0.0.0";
+          Port = cfg.port;
+          DataFolder = cfg.dataDir;
+          MusicFolder = cfg.musicDir;
+          EnableSharing = cfg.enableSharing;
+        };
+      };
+    })
+  ];
+}