CSS navbar and color tweaks (#13609)

* CSS and color tweaks

- Unify navbar-style menus
- Fix admin bar overlapping menu bar
- Fixes file edit comment box
- Fix double border on review box
- Fix review timeline icons

* Many fixes to new-menu and navbar layout enhancements

* misc settings fixes

* navbar tweak

* fix pr tabs

* branch tag and arc color tweaks

web_src/less/_explore.less

@@ -1,12 +1,9 @@
 .explore {
-  padding-top: 15px;
-
   .navbar {
     justify-content: center;
     padding-top: 15px !important;
-    margin-top: -15px !important;
     margin-bottom: 15px !important;
-    background-color: #fafafa !important;
+    background-color: var(--color-navbar) !important;
     border-width: 1px !important;
 
     .svg {