feat: add Nix flake for reproducible builds and deployment

- Add flake.nix with packages for all 5 apps (landing, gacha, backoffice, dimentorin, hackathon)
- Add NixOS modules for deployment (systemd service for Next.js, nginx for Vite apps)
- Add mkHackathonWithEnv function for build-time environment variables
- Add development shell with Node.js 22, npm, bun

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

nix/modules/landing.nix

@@ -0,0 +1,83 @@
+# NixOS Module for Imphnen Landing
+{ self }:
+
+{ config, lib, pkgs, ... }:
+
+let
+  cfg = config.services.imphnen-landing;
+in {
+  options.services.imphnen-landing = {
+    enable = lib.mkEnableOption "Imphnen Landing Page";
+
+    port = lib.mkOption {
+      type = lib.types.port;
+      default = 3000;
+      description = "Port to run the landing server on";
+    };
+
+    hostname = lib.mkOption {
+      type = lib.types.str;
+      default = "0.0.0.0";
+      description = "Hostname to bind to";
+    };
+
+    package = lib.mkOption {
+      type = lib.types.package;
+      default = self.packages.${pkgs.system}.landing;
+      description = "The landing package to use";
+    };
+
+    openFirewall = lib.mkOption {
+      type = lib.types.bool;
+      default = false;
+      description = "Open firewall for the landing port";
+    };
+
+    environmentFile = lib.mkOption {
+      type = lib.types.nullOr lib.types.path;
+      default = null;
+      description = "Environment file for secrets";
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    systemd.services.imphnen-landing = {
+      description = "Imphnen Landing Page";
+      wantedBy = [ "multi-user.target" ];
+      after = [ "network.target" ];
+
+      environment = {
+        NODE_ENV = "production";
+        PORT = toString cfg.port;
+        HOSTNAME = cfg.hostname;
+      };
+
+      serviceConfig = {
+        Type = "simple";
+        ExecStart = "${cfg.package}/bin/imphnen-landing";
+        Restart = "on-failure";
+        RestartSec = "5s";
+
+        # Hardening
+        DynamicUser = true;
+        NoNewPrivileges = true;
+        ProtectSystem = "strict";
+        ProtectHome = true;
+        PrivateTmp = true;
+        ProtectKernelTunables = true;
+        ProtectKernelModules = true;
+        ProtectControlGroups = true;
+        RestrictAddressFamilies = [ "AF_INET" "AF_INET6" "AF_UNIX" ];
+        RestrictNamespaces = true;
+        LockPersonality = true;
+        MemoryDenyWriteExecute = true;
+        RestrictRealtime = true;
+        RestrictSUIDSGID = true;
+      } // lib.optionalAttrs (cfg.environmentFile != null) {
+        EnvironmentFile = cfg.environmentFile;
+      };
+    };
+
+    networking.firewall.allowedTCPPorts = lib.mkIf cfg.openFirewall [ cfg.port ];
+  };
+}

nix/modules/static-app.nix

@@ -0,0 +1,76 @@
+# NixOS Module for Static Vite Apps (nginx-based)
+{ self }:
+
+{ appName }:
+
+{ config, lib, pkgs, ... }:
+
+let
+  cfg = config.services."imphnen-${appName}";
+in {
+  options.services."imphnen-${appName}" = {
+    enable = lib.mkEnableOption "Imphnen ${appName}";
+
+    domain = lib.mkOption {
+      type = lib.types.str;
+      description = "Domain name for the app";
+    };
+
+    package = lib.mkOption {
+      type = lib.types.package;
+      default = self.packages.${pkgs.system}.${appName};
+      description = "The ${appName} package to use";
+    };
+
+    enableSSL = lib.mkOption {
+      type = lib.types.bool;
+      default = true;
+      description = "Enable ACME SSL";
+    };
+
+    extraLocations = lib.mkOption {
+      type = lib.types.attrsOf lib.types.anything;
+      default = {};
+      description = "Additional nginx locations";
+    };
+
+    extraConfig = lib.mkOption {
+      type = lib.types.lines;
+      default = "";
+      description = "Extra nginx configuration";
+    };
+  };
+
+  config = lib.mkIf cfg.enable {
+    services.nginx = {
+      enable = true;
+      recommendedGzipSettings = true;
+      recommendedOptimisation = true;
+      recommendedProxySettings = true;
+      recommendedTlsSettings = true;
+
+      virtualHosts.${cfg.domain} = {
+        forceSSL = cfg.enableSSL;
+        enableACME = cfg.enableSSL;
+        root = cfg.package;
+
+        locations = {
+          "/" = {
+            tryFiles = "$uri $uri/ /index.html";
+          };
+
+          # Cache static assets
+          "~* \\.(js|css|png|jpg|jpeg|gif|ico|svg|woff|woff2|ttf|eot)$" = {
+            tryFiles = "$uri =404";
+            extraConfig = ''
+              expires 1y;
+              add_header Cache-Control "public, immutable";
+            '';
+          };
+        } // cfg.extraLocations;
+
+        extraConfig = cfg.extraConfig;
+      };
+    };
+  };
+}