add config reset command and bootstrap --clean flag

[Esity]

Summary

• Add legionio config reset subcommand to wipe all *.json from ~/.legionio/settings/ (prompts for confirmation unless --force)
• Add --clean flag to legionio bootstrap to clear settings before import
• Skip ConfigScaffold.run during bootstrap when a source is provided — scaffolded empty files were silently conflicting with imported config

Closes #88

Test plan

• bundle exec rspec spec/cli/config_reset_spec.rb — 12 examples, 0 failures
• bundle exec rspec spec/cli/bootstrap_command_spec.rb — 69 examples, 0 failures
• Full suite: 4084 examples, 0 failures
• bundle exec rubocop on all changed files — 0 offenses