Upgrade to Ruby 4.0.1 and Rails 8.1.2

Amp-Thread-ID: https://ampcode.com/threads/T-019c4621-696a-76e3-848c-48fdd9c271ae
Co-authored-by: Amp <amp@ampcode.com>

Author: mitchbne

.ruby-version

@@ -1 +1 @@
-3.4.1
+4.0.1

.tool-versions

@@ -1 +1 @@
-ruby 3.4.1
+ruby 4.0.1

Gemfile

@@ -1,10 +1,10 @@
 source 'https://rubygems.org'
 git_source(:github) { |repo| "https://github.com/#{repo}.git" }
 
-ruby '3.4.1'
+ruby '4.0.1'
 
 # Bundle edge Rails instead: gem "rails", github: "rails/rails", branch: "main"
-gem "rails", "~> 8.0.2"
+gem "rails", "~> 8.1.2"
 # The modern asset pipeline for Rails [https://github.com/rails/propshaft]
 gem "propshaft"
 # Use sqlite3 as the database for Active Record