v4.1.0

• Parse attachment filenames from both MIME parameters and disposition parameters.
• Decode MIME part bodies with the standard base64 and quoted-printable decoders.
• Expose content IDs and fail clearly when IMAP structure or body fetching fails.
• Add injectable structure and body fetchers for reliable testing and custom integrations.
• Verify compatibility from PHP 5.4 through PHP 8.5 without raising the package minimum.