Add Nix dev shell with local MariaDB and dev orchestration script

flake.nix

@@ -0,0 +1,33 @@
+{
+  description = "Dev shell for think.greaterchiangmai.com (frontend + backend Laravel apps)";
+
+  inputs.nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+
+  outputs = { self, nixpkgs }:
+    let
+      systems = [ "x86_64-linux" "aarch64-linux" "x86_64-darwin" "aarch64-darwin" ];
+      forAll = f: nixpkgs.lib.genAttrs systems (system: f nixpkgs.legacyPackages.${system});
+    in
+    {
+      devShells = forAll (pkgs:
+        let
+          php = pkgs.php83;
+        in
+        {
+          default = pkgs.mkShell {
+            packages = [
+              php
+              php.packages.composer
+              pkgs.mariadb
+              pkgs.nodejs_22
+            ];
+
+            shellHook = ''
+              export DEV_ROOT="$PWD"
+              export PATH="$DEV_ROOT/dev:$PATH"
+              echo "think-greaterchiangmai dev shell — run 'dev help'"
+            '';
+          };
+        });
+    };
+}