Drop Rails.application.secrets in favor of credentials/ENV

Rails 7.2 removes Rails.application.secrets entirely. Anything that
relied on config/secrets.yml stops working at the bump. Currently the
file only carries secret_key_base, which Rails resolves through this
chain (in order):

  1. Rails.application.credentials.secret_key_base
  2. ENV["SECRET_KEY_BASE"]
  3. tmp/local_secret.txt (dev/test auto-generated)

Production already uses ENV["SECRET_KEY_BASE"] (unchanged). Dev/test
fall through to tmp/local_secret.txt automatically, so deleting
secrets.yml is safe.

Also drops config.read_encrypted_secrets = true from production.rb,
which is a no-op in 7.2 and only ever applied to the legacy
secrets.yml.enc workflow.

Ref: https://guides.rubyonrails.org/upgrading_ruby_on_rails.html#rails-application-secrets-removal

Author: JuanVqz

config/environments/production.rb

@@ -14,11 +14,6 @@
   config.consider_all_requests_local = false
   config.action_controller.perform_caching = true
 
-  # Attempt to read encrypted secrets from `config/secrets.yml.enc`.
-  # Requires an encryption key in `ENV["RAILS_MASTER_KEY"]` or
-  # `config/secrets.yml.key`.
-  config.read_encrypted_secrets = true
-
   # Disable serving static files from the `/public` folder by default since
   # Apache or NGINX already handles this.
   config.public_file_server.enabled = ENV["RAILS_SERVE_STATIC_FILES"].present?