Upgrade Ruby and application dependencies

[flemzord]

What changed

• Upgrade Ruby from 3.4.7 to 3.4.10.
• Upgrade Rails from 8.1.0 to 8.1.3.
• Upgrade Puma from 6.6.1 to 7.2.1.
• Refresh all gems allowed by the current dependency constraints, including Nokogiri, Rack, RQRCode, bcrypt, net-imap, websocket-driver, SimpleCov, and Standard Ruby.
• Adapt the SimpleCov configuration to its current API.
• Fix the newly enforced Standard Ruby redundant-self violation.

Why

The lockfile was behind current maintenance and security releases. Rails 8.1.3 includes the latest Rails 8.1 bug and security fixes. Puma 7.2.1 addresses CVE-2026-47736 and CVE-2026-47737, which remained vulnerable under the previous Puma 6 constraint.

Security impact

The default branch currently reports 63 Dependabot alerts across the Ruby bundle. The updated lockfile passes bundler-audit with no known vulnerabilities.

Validation

• Docker image builds successfully with Ruby 3.4.10.
• 448 RSpec examples, 0 failures.
• standardrb passes.
• bundle outdated reports the bundle is up to date within declared constraints.
• bundle-audit check reports no vulnerabilities.