feat(core): initialize NaxOS declarative NixOS distribution, modules, and ISO installer

modules/services/apps/nextcloud.nix

@@ -0,0 +1,43 @@
+{ config, pkgs, lib, ... }:
+
+with lib;
+
+let
+  cfg = config.services.naxos.apps.nextcloud;
+in {
+  options.services.naxos.apps.nextcloud = {
+    enable = mkEnableOption "Nextcloud Personal Cloud & Collaboration Platform";
+
+    hostName = mkOption {
+      type = types.str;
+      default = "cloud.local";
+      description = "Domain / hostname for Nextcloud.";
+    };
+
+    homeDir = mkOption {
+      type = types.str;
+      default = "/tank/data/nextcloud";
+      description = "Persistent data directory on ZFS storage.";
+    };
+
+    adminpassFile = mkOption {
+      type = types.nullOr types.str;
+      default = null;
+      description = "Path to file containing initial admin password.";
+    };
+  };
+
+  config = mkIf cfg.enable {
+    services.nextcloud = {
+      enable = true;
+      hostName = cfg.hostName;
+      home = cfg.homeDir;
+      config = {
+        adminuser = "admin";
+        adminpassFile = cfg.adminpassFile;
+        dbtype = "sqlite";
+      };
+      caching.redis = true;
+    };
+  };
+}