Fix mutt's urlscan and HTML view macros

Use <pipe-message> for urlscan (pipe-entry doesn't exist in the pager) and bind it in the index too. Open HTML attachments in Zen instead of Vivaldi, from ~/.cache/mutt/html, which the firejail profiles share. Prune cached messages deleted on the server.

.config/mutt/macros

@@ -1,3 +1,3 @@
-macro pager \cb <pipe-entry>'urlscan'<enter> 'Follow links with urlview'
+macro index,pager \cb "<pipe-message>urlscan<enter>" "Follow links with urlscan"
 macro index,pager   a "<pipe-message>abook --add-email-quiet<return>" "Add this sender to Abook"
-macro attach V "<pipe-entry>iconv -c --to-code=UTF8 > ~/.cache/mutt/mail.html<enter><shell-escape>vivaldi-stable ~/.cache/mutt/mail.html<enter>"
+macro attach V "<pipe-entry>iconv -c --to-code=UTF8 > ~/.cache/mutt/html/mail.html<enter><shell-escape>zen-browser ~/.cache/mutt/html/mail.html >/dev/null 2>&1<enter>" "Open attachment in Zen"

.config/mutt/muttrc

@@ -29,6 +29,7 @@ bind editor         <Tab> complete-query
 # Other settings
 set header_cache     = "~/.cache/mutt"
 set message_cachedir = "~/.cache/mutt"
+set message_cache_clean = yes
 
 set timeout          = 30
 set editor           = "vim"