feat: nicer smart filters & folders theme (#795)

* fix: color add button and drop

* fix: color scrollbars

* fix: remove infinite scroll and fix scrollbars

* fix: plus icon center

* fix: navigation padding, structure simplif and naming

* fix: simplify scrollbars

* fix: scroll bar simplif + scheme in macos

* fix: magic variables to const

* refactor: extract panel ref state

* refactor: remove dead code, simple macos theme

app/assets/stylesheets/_main.scss

@@ -203,11 +203,6 @@ $footer-height: 2rem;
     position: relative;
     overflow: hidden;
 
-    .scrollable {
-      overflow-y: auto;
-      overflow-x: hidden;
-    }
-
     > .content {
       height: 100%;
       max-height: 100%;