feat(email): implement SMTP send with confirmation and resend functio…

[canaria-computer]

…nality

• Add send-with-confirm subcommand with interactive/stdin modes

  • Interactive mode: prompts for recipients with pre-filled From/Reply-To
  • Stdin mode: reads recipients from stdin for CI/CD automation
  • Email preview before sending with confirmation prompt
  • Automatic .eml save on send failure

• Add resend subcommand for failed email retry

  • Load and resend previously saved .eml files
  • Support recipient editing and Message-ID regeneration
  • Preserve original message structure

• Implement SMTP sender with retry logic

  • 3 retry attempts with exponential backoff (1s→2s→4s)
  • Automatic transient error detection and retry
  • Support AUTH types: AUTO, PLAIN, LOGIN, CRAM-MD5
  • Support encryption: SSL/TLS, STARTTLS, None

• Add email placeholder expansion in interactive mode

  • Expand {report_id} in From/Reply-To addresses before display
  • Placeholders resolved from report directory context

• Fix config key mapping inconsistency

  • Map email.mime.type to email.mime_type in env var transformation
  • Unify mime type configuration across file/env sources

• Add SMTP documentation (doc/email-smtp.md)

  • Comprehensive usage guide for send-with-confirm and resend
  • SMTP URI format and percent encoding examples
  • Configuration methods and security best practices
  • CI/CD integration examples (GitHub Actions, GitLab CI, Jenkins)
  • Troubleshooting guide and FAQ

• Add debug logging for multipart/alternative email generation

  • Log MimeType config value and includeHTML decision
  • Log email body format (HTML+text vs text-only)