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/webapp/src/main/elm/App/Data.elm

@@ -6,6 +6,7 @@ module App.Data exposing
     )
 
 import Api.Model.AuthResult exposing (AuthResult)
+import Api.Model.BasicResult exposing (BasicResult)
 import Api.Model.VersionInfo exposing (VersionInfo)
 import Browser exposing (UrlRequest)
 import Browser.Navigation exposing (Key)
@@ -45,6 +46,7 @@ type alias Model =
     , userMenuOpen : Bool
     , subs : Sub Msg
     , uiSettings : UiSettings
+    , sidebarVisible : Bool
     }
 
 
@@ -92,6 +94,7 @@ init key url flags_ settings =
       , userMenuOpen = False
       , subs = Sub.none
       , uiSettings = settings
+      , sidebarVisible = settings.sideMenuVisible
       }
     , Cmd.batch
         [ Cmd.map UserSettingsMsg uc
@@ -145,6 +148,8 @@ type Msg
     | ToggleNavMenu
     | ToggleUserMenu
     | GetUiSettings UiSettings
+    | ToggleSidebar
+    | ToggleDarkMode
 
 
 defaultPage : Flags -> Page