Use flakes vs devbox (#723)

Reviewed-on: https://gitea.com/gitea/tea/pulls/723
Co-authored-by: techknowlogick <techknowlogick@gitea.com>
Co-committed-by: techknowlogick <techknowlogick@gitea.com>

flake.nix

@@ -0,0 +1,30 @@
+{
+  description = "Tea - A command line tool to interact with Gitea";
+
+  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; };
+      in
+      {
+        devShells.default = pkgs.mkShell {
+          name = "tea-dev-environment";
+          buildInputs = with pkgs; [
+            go_1_24
+            gopls
+            gnumake
+            # Add other dependencies here if needed
+          ];
+
+          shellHook = ''
+            echo 'Welcome to tea. Check out the Makefile for runnable targets.'
+          '';
+        };
+      }
+    );
+}