docs: align Go version in README and CONTRIBUTING with go.mod (1.26.3)

README badge and prerequisites listed Go 1.21.12 / 1.23.9 in different
places, but go.mod requires Go 1.26.3. Bring the docs in sync so new
contributors install a toolchain that can actually build the node.

CONTRIBUTING.md

@@ -4,7 +4,7 @@ Thank you for your interest in contributing to Lux Node! This document provides
 
 To start developing on Lux Node, you'll need a few things installed.
 
-- Golang version >= 1.23.9
+- Golang version >= 1.26.3
 - gcc
 - g++
 
@@ -34,7 +34,7 @@ We are committed to fostering a welcoming and inclusive community. Please be res
 
 ### Prerequisites
 
-- Go 1.21.12 or higher
+- Go 1.26.3 or higher
 - Git
 - Make
 - GCC/G++ compiler

README.md

@@ -5,7 +5,7 @@
 ---
 
 [![Build Status](https://github.com/luxfi/node/actions/workflows/ci.yml/badge.svg)](https://github.com/luxfi/node/actions)
-[![Go Version](https://img.shields.io/badge/go-1.21.12-blue.svg)](https://golang.org/)
+[![Go Version](https://img.shields.io/badge/go-1.26.3-blue.svg)](https://golang.org/)
 [![License](https://img.shields.io/badge/license-BSD--3--Clause-blue.svg)](LICENSE)
 
 Node implementation for the [Lux](https://lux.network) network -
@@ -38,7 +38,7 @@ The minimum recommended hardware specification for nodes connected to Mainnet is
 
 If you plan to build Lux Node from source, you will also need the following software:
 
-- [Go](https://golang.org/doc/install) version >= 1.23.9
+- [Go](https://golang.org/doc/install) version >= 1.26.3
 - [gcc](https://gcc.gnu.org/)
 - g++