RewriteEngine on
RewriteCond %{HTTP_HOST} ^baikal.example.com$ [NC,OR]
RewriteCond %{REQUEST_URI} !html/
RewriteRule .well-known/carddav /dav.php [R,L]
RewriteRule .well-known/caldav /dav.php [R,L]
RewriteRule (.*) /html/$1 [L]