Point Gemfile.next at Rails 8.0 (7.2 -> 8.0 hop)

[JuanVqz]

What

Advances the dual boot one hop: promote the previous next target to current and open the next hop.

• current (else): Rails 7.1 -> 7.2 (locked at 7.2.3.1)
• next (if next?): Rails 7.2 -> 8.0 (locked at 8.0.5)

Both Gemfile.lock and Gemfile.next.lock regenerated via bundle update rails; each resolved cleanly with no conflicts.

Deprecation cleanup

Two deprecations surfaced booting/precompiling under 8.0; both fixed here:

1. config.read_encrypted_secrets = true (production.rb) drove the legacy encrypted-secrets feature (config/secrets.yml.enc), removed alongside config/secrets.yml back in 7.2. It warns on 7.2 (deprecated and will be removed in Rails 8.0) and is a silent no-op on 8.0 -- dead config either way. Removed the line and its comment block. No secrets.yml.enc / credentials in the app, so nothing to migrate.
2. to_time timezone preservation: under load_defaults 7.1, ActiveSupport hasn't opted into the 8.1 default, so 8.0 warns at boot. Set config.active_support.to_time_preserves_timezone = :zone in application.rb. Verified the value is accepted on both 7.2.3.1 and 8.0.5, so it's set unconditionally (no dual-boot branch).

Other

• docker/entrypoint.sh: dropped the 5-attempt db:prepare retry loop for a single bundle exec rails db:prepare.
• .gitignore: ignore /vendor/bundle_localtest (the host-side BUNDLE_PATH used to run the suite against both Gemfiles without rebuilding the Docker image).

Verification

Run on the host (asdf ruby 3.2.11, matching the Gemfile) against an ephemeral Postgres 16.13:

• Gemfile (7.2.3.1): boot OK, production boot clean (zero deprecation warnings), suite green -- 16 runs, 52 assertions, 0 failures, 0 errors.
• Gemfile.next (8.0.5): boot OK, production boot clean (zero deprecation warnings), suite green -- 16 runs, 52 assertions, 0 failures, 0 errors.

The detection patterns for both deprecations are added to the rails-upgrade skill in ombulabs/claude-code_rails-upgrade-skill#122.