Transactional emails share branded shell; digest renders markdown

Changed

• Transactional emails now share a unified branded shell — digest, magic link, password reset, verification, and operator alerts all use the same design; release bodies in digest emails now render markdown correctly instead of showing raw asterisks.
• Email subject lines carry more context — digest subjects name the leading orgs; magic-link and password-reset subjects include expiry times; operator alerts include the name of the affected source or org.