This drops fomantic-ui as css toolkit and introduces tailwindcss. With
tailwind there are no predefined components, but it's very easy to
create those. So customizing the look&feel is much simpler, most of
the time no additional css is needed.
This requires a complete rewrite of the markup + styles. Luckily all
logic can be kept as is. The now old ui is not removed, it is still
available by using a request header `Docspell-Ui` with a value of `1`
for the old ui and `2` for the new ui.
Another addition is "dev mode", where docspell serves assets with a
no-cache header, to disable browser caching. This makes developing a
lot easier.
Mails are filtered once by using an imap search and then by some globs
to filter files and subjects. Imap can search by subject via a
string-contains, but not via globs or patterns (afaik). The subject
filter is applied to all downloaded mail headers. Now for post
processing (moving to some target folder or deleting), it can be
chosen to post-process all "seen" mails or only those that matched all
filters.
