Protect exception reports from sensitive data.

[samuel-williams-shopify]

Summary

• redact sensitive request headers, query parameters, session state, and controller variables by default
• omit the raw query string from the report request line
• make request body attachments opt-in with dump_body: true
• bound body and environment attachments with attachment_size_limit
• make dump_environment: false exclude application state from the report body

Verification

• bundle exec sus test/utopia/exceptions/mailer.rb (15 tests, 47 assertions)
• bundle exec rubocop lib/utopia/exceptions/mailer.rb test/utopia/exceptions/mailer.rb
• bundle exec bake decode:index:coverage lib
• git diff --check

The full local suite reached 482 passing tests. Its four command-generation tests remain blocked by the existing stale vendor/bundle native extensions and unavailable locally installed protocol-url dependency; CI runs those tests with a clean bundle.