build: add nix flake for dev environment (#17)

Author: tembleking

.envrc

@@ -0,0 +1,4 @@
+has nix && use flake
+watch_file *.nix
+dotenv_if_exists .env # You can create a .env file with your env vars for this project. You can also use .secrets if you are using act. See the line below.
+dotenv_if_exists .secrets # Used by [act](https://nektosact.com/) to load secrets into the pipelines

.gitignore

@@ -70,3 +70,8 @@ target/
 
 # VSCode
 .vscode/
+
+# Nix development
+.direnv/
+.secrets
+result

flake.lock

@@ -0,0 +1,35 @@
+{
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+  outputs =
+    {
+      self,
+      nixpkgs,
+      flake-utils,
+    }:
+    flake-utils.lib.eachDefaultSystem (
+      system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+          config.allowUnfree = true;
+        };
+      in
+      {
+        devShells.default =
+          with pkgs;
+          mkShell {
+            packages = [
+              python3
+              uv
+              ruff
+              basedpyright
+            ];
+          };
+
+        formatter = pkgs.nixfmt-rfc-style;
+      }
+    );
+}