Preview and automation polish
Improvements
- Webview previews render custom fonts more reliably.
- Automation processing has more predictable retry behavior.
Fixes
- Newsletter website redirects work correctly again.
- Inline code is escaped correctly in Markdown-rendered mails.
- Sending a test email no longer saves draft changes unexpectedly.
- Starting an invalid automation now shows a notification instead of an error page.
- Subscriber imports are skipped cleanly when their list was deleted.
- Invalid email addresses are handled more accurately as permanent bounces.