First version of new ui based on tailwind

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.

modules/joex/src/main/scala/docspell/joex/Main.scala

@@ -5,7 +5,7 @@ import java.nio.file.{Files, Paths}
 import cats.effect._
 import cats.implicits._
 
-import docspell.common.{Banner, Pools, ThreadFactories}
+import docspell.common._
 
 import org.log4s._
 
@@ -50,6 +50,10 @@ object Main extends IOApp {
       Some(cfg.fullTextSearch.solr.url).filter(_ => cfg.fullTextSearch.enabled)
     )
     logger.info(s"\n${banner.render("***>")}")
+    if (EnvMode.current.isDev) {
+      logger.warn(">>>>>   Docspell is running in DEV mode!   <<<<<")
+    }
+
     val pools = for {
       cec <- connectEC
       bec <- blockingEC