Add file upload and download (zip for directories)

Frontend/src/Styles/Theme.css

@@ -227,6 +227,10 @@ img,
   line-height: 1;
   font-size: 11px;
   cursor: pointer;
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  text-decoration: none;
 }
 
 .TreeRowActionButton:hover {
@@ -309,6 +313,13 @@ img,
   padding: 8px 0;
 }
 
+.DirectoryList.DraggingOver,
+.SidebarTree.DraggingOver {
+  outline: 2px dashed var(--Purple);
+  outline-offset: -2px;
+  background: var(--SurfaceAlt);
+}
+
 .DirectoryEntry {
   display: flex;
   align-items: center;
@@ -370,6 +381,21 @@ img,
   cursor: default;
 }
 
+.DownloadButton {
+  background: var(--SurfaceAlt);
+  color: var(--Text);
+  border: 1px solid var(--Purple);
+  border-radius: 4px;
+  padding: 4px 10px;
+  font-family: inherit;
+  cursor: pointer;
+  text-decoration: none;
+}
+
+.DownloadButton:hover {
+  background: var(--Border);
+}
+
 .SaveErrorText {
   color: var(--Red);
   align-self: center;