Update keela gem to 0.4.1

What does this MR do and why?

Updates the keela gem from 0.3.0 to 0.4.1.

Release highlights

0.4.1 - Bug fixes

• Constants used as hash keys (CONST => value) or in rescue splats (rescue *ERRORS => e) are now correctly detected as used
• Methods referenced as literal symbols (:method_name) are now detected as used, including Rails callbacks, send(:method), validate :method, etc.
• I18n pluralization keys (one, other, zero, etc.) are now detected as used when the parent key is called with t('key', count: n)
• I18n lazy lookup (t('.title') in views) now correctly resolves to the full key based on the view path

0.4.0 - New features

• Verbose mode (--verbose) to show files being scanned, glob patterns, and configuration for debugging
• Source location (--source-location) to show line numbers in reports for easier navigation
• Exclusion validation (--test-exclusions) to find stale entries in exclusion files
• TOON output format (--format toon) for token-efficient LLM-friendly output
• Configurable definition paths per strategy via strategies.<name>.definition_paths in config file
• Multi-method delegate declarations now detect all methods, not just the first
• Class methods (def self.foo) are now correctly detected as unused

Full changelog: https://github.com/kerrizor/keela/blob/main/CHANGELOG.md

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

How to set up and validate locally

bundle install
bundle exec keela --help

Changelog: other