Make sure the whole file list header is sticky and properly stacks to other headers

Signed-off-by: Julius Härtl <jus@bitgrid.net>

apps/files/css/files.scss

@@ -65,26 +65,22 @@
 	#emptycontent:not(.hidden) ~ & {
 		display: none;
 	}
-}
-
-#filestable.hidden {
-	display: none;
-}
-
-@media only screen and (min-width: $breakpoint-mobile + 1) {
-	#filestable {
 	// floating header
 	thead {
 		position: -webkit-sticky;
 		position: sticky;
+		@include position('sticky');
 		// header + breadcrumbs
 		top: $header-height;
 		// under breadcrumbs, over file list
-			z-index: 55;
+		z-index: 60;
 		display: block;
 		background-color: var(--color-main-background-translucent);
 	}
-	}
+}
+
+#filestable.hidden {
+	display: none;
 }
 
 /* fit app list view heights */
@@ -289,14 +285,8 @@ table th.column-last, table td.column-last {
 	max-width: 130px;
 }
 
-/* Multiselect bar */
-table.multiselect thead {
-	@include position('sticky');
+#app-content-files thead {
 	top: 94px;
-	z-index: 55;
-	-moz-box-sizing: border-box;
-	box-sizing: border-box;
-	left: $navigation-width;
 }
 
 table.multiselect thead th {
@@ -309,7 +299,7 @@ table.multiselect thead th {
 }
 
 table.multiselect #headerName {
-	position: sticky;
+	position: relative;
 	width: 9999px; /* when we use 100%, the styling breaks on mobile … table styling */
 }
 table.multiselect #modified {