[PB-6787] feature/Send the body of an email as markup instead of plain text

[CandelR]

Send the body of an email as markup and render decrypted markup bodies

Summary

• mailCrypto.service.ts: encryptAndSendEmail and encryptAndSendReply wrap the body with plainTextToHtml before encrypting it, because the envelope carries a single body that mail-web and mail-server both treat as HTML.encryptMessageForRecipients now takes that markup as body, while preview stays plain text for the mailbox list.
• emailBodyContent.ts: new isMarkupBody tells whether a decrypted body is markup . resolveEmailBody uses it, so a decrypted HTML body is sanitised and rendered instead of shown with its tags escaped. escapeHtml is exported and plainTextToHtml builds on it.
• EmailBody.tsx: a message that could not be decrypted shows a notice instead of an empty body

[sonarqubecloud]

Quality Gate failed

Failed conditions
26.5% Duplication on New Code (required ≤ 3%)

See analysis details on SonarQube Cloud