src/themes/cgspace: import scss from dspace theme

Instead of copying the entire SCSS and having to keep it in sync
with upstream changes, just import the styles and override what
we need.

src/themes/cgspace/app/header/header.component.scss

@@ -1,28 +1,6 @@
-@media screen and (min-width: map-get($grid-breakpoints, md)) {
-  nav.navbar {
-    display: none;
-  }
-}
+@import '../../../dspace/app/header/header.component.scss';
 
-/* always set header background, not only on medium size screens! */
+// The dspace theme only sets the header background on medium screens and up
 .header {
   background-color: var(--ds-header-bg);
 }
-
-.navbar-brand img {
-  @media screen and (max-width: map-get($grid-breakpoints, md)) {
-    height: var(--ds-header-logo-height-xs);
-  }
-}
-.navbar-toggler .navbar-toggler-icon {
-  background-image: none !important;
-  line-height: 1.5;
-}
-
-.navbar-toggler {
-  color: var(--ds-header-icon-color);
-
-  &:hover, &:focus {
-    color: var(--ds-header-icon-color-hover);
-  }
-}

src/themes/cgspace/app/navbar/navbar.component.scss

@@ -1,61 +1,12 @@
-nav.navbar {
-  // Ignore this style from the dspace theme because it creates a white gap
-  //border-top: 1px var(--ds-header-navbar-border-top-color) solid;
-  border-bottom: 5px var(--ds-header-navbar-border-bottom-color) solid;
-  align-items: baseline;
-  color: var(--ds-header-icon-color);
-}
-
-/** Mobile menu styling **/
-@media screen and (max-width: map-get($grid-breakpoints, md)-0.02) {
-  .navbar {
-    width: 100vw;
-    background-color: var(--bs-white);
-    position: absolute;
-    overflow: hidden;
-    height: 0;
-    &.open {
-      height: 100vh; //doesn't matter because wrapper is sticky
-    }
-  }
-}
-
-@media screen and (min-width: map-get($grid-breakpoints, md)) {
-  .reset-padding-md {
-    margin-left: calc(var(--bs-spacer) / -2);
-    margin-right: calc(var(--bs-spacer) / -2);
-  }
-}
+@import '../../../dspace/app/navbar/navbar.component.scss';
 
-/* TODO remove when https://github.com/twbs/bootstrap/issues/24726 is fixed */
-.navbar-expand-md.navbar-container {
-  @media screen and (max-width: map-get($grid-breakpoints, md)-0.02) {
-    > .navbar-inner-container {
-      padding: 0 var(--bs-spacer);
-      a.navbar-brand {
-        display: none;
-      }
-      .navbar-collapsed {
-        display: none;
-      }
-    }
-    padding: 0;
-  }
-  height: 80px;
-}
-
-a.navbar-brand img {
-  max-height: var(--ds-header-logo-height);
+nav.navbar {
+  // Override this style from the dspace theme because it creates a white gap
+  // on mobile.
+  border-top: none;
 }
 
 .navbar-nav {
-  ::ng-deep a.nav-link {
-    color: var(--ds-navbar-link-color);
-  }
-  ::ng-deep a.nav-link:hover {
-    color: var(--ds-navbar-link-color-hover);
-  }
-
   ::ng-deep ul a.nav-link {
     color: var(--ds-home-news-link-color);
   }