chore: change port to 1234 and add Makefile/flake.nix

- Change dev server port from 1312 to 1234
- Add Makefile for common development commands
- Add flake.nix for Nix development environment

flake.nix

@@ -0,0 +1,34 @@
+{
+  description = "Code Crispies - Interactive CSS/HTML/Tailwind learning platform";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = nixpkgs.legacyPackages.${system};
+      in {
+        devShells.default = pkgs.mkShell {
+          buildInputs = with pkgs; [
+            nodejs_20
+            nodePackages.npm
+            gnumake
+          ];
+
+          shellHook = ''
+            echo "Code Crispies Development Environment"
+            echo ""
+            echo "Commands:"
+            echo "  make dev     - Start dev server (port 1234)"
+            echo "  make build   - Production build"
+            echo "  make test    - Run tests"
+            echo "  make format  - Format code"
+            echo ""
+          '';
+        };
+      }
+    );
+}