Cut current boot over to Rails 8.0 and adopt 8.0 schema format

[JuanVqz]

What

Rails 8.0 is now the production version, so this completes the cutover: point the current (else) boot at 8.0 as well. Both boots now resolve to Rails 8.0.5.

• Gemfile: else branch >= 7.2.0, < 7.3.0 -> >= 8.0.0, < 8.1.0 (matches the next? branch).
• Gemfile.lock regenerated via bundle update rails (7.2.3.1 -> 8.0.5). Gemfile.next.lock was already 8.0.5.

The dual-boot scaffold (next?, the Gemfile.next symlink, the web_next service) is kept intact so the next hop only needs to bump the next? branch. The now-identical branches are wrapped in a rubocop:disable Style/IdenticalConditionalBranches.

Schema (db/schema.rb)

Adopt the Rails 8.0 schema-dumper format:

• ActiveRecord::Schema[7.1] -> [8.0]
• enable_extension "plpgsql" -> "pg_catalog.plpgsql" (8.0 dumps schema-qualified extension names)

Deliberately keeps t.integer "file_file_size" rather than the bigint a fresh migrate would emit. That bigint comes from kt-paperclip's t.attachment macro (old paperclip used integer), not from Rails 8, and production's column -- created years ago under paperclip -- is still integer. Keeping integer keeps schema.rb faithful to production. A db:schema:load + dump round-trips cleanly with no churn (verified). Note: this schema is used for new/test/CI databases via schema:load; production is unaffected either way.

Verification

Host, asdf ruby 3.2.11, against Postgres 16.13:

• db:schema:load succeeds on the 8.0-format schema; re-dump preserves integer.
• Production boot clean -- zero deprecation warnings.
• Suite green -- 16 runs, 52 assertions, 0 failures, 0 errors.