feat: add health server and prometheus metrics to worker

Gemfile

@@ -21,12 +21,14 @@ gem "mysql2"
 gem "nifty-utils"
 gem "nilify_blanks"
 gem "nio4r"
+gem "prometheus-client"
 gem "puma"
 gem "rails", "= 7.0.8.1"
 gem "resolv"
 gem "secure_headers"
 gem "sentry-rails"
 gem "turbolinks", "~> 5"
+gem "webrick"
 
 group :development, :assets do
   gem "coffee-rails", "~> 5.0"