Improve same-window folder drops

server/public/styles.css

@@ -255,6 +255,7 @@
 .u-nav .file-row:hover,
 .u-nav .file-row.selected,
 .u-nav .file-row.dragging,
+.u-nav .file-row.drop-candidate,
 .u-nav .file-row.drop-target {
   background: var(--surface-2);
 }
@@ -262,10 +263,15 @@
 .u-nav .file-row:hover td,
 .u-nav .file-row.selected td,
 .u-nav .file-row.dragging td,
+.u-nav .file-row.drop-candidate td,
 .u-nav .file-row.drop-target td {
   background: var(--surface-2) !important;
 }
 
+.u-nav .file-row.drop-candidate td:first-child {
+  box-shadow: inset 3px 0 0 color-mix(in srgb, var(--accent) 72%, transparent);
+}
+
 .u-nav .file-row {
   -webkit-user-drag: none;
   user-select: none;
@@ -327,16 +333,22 @@
 .u-nav .icon-item:hover,
 .u-nav .icon-item.selected,
 .u-nav .icon-item.dragging,
+.u-nav .icon-item.drop-candidate,
 .u-nav .icon-item.drop-target {
   background: var(--surface-2);
   border-color: var(--line);
 }
 
 .u-nav .icon-item.selected,
+.u-nav .icon-item.drop-candidate,
 .u-nav .icon-item.drop-target {
   border-color: var(--accent);
 }
 
+.u-nav .icon-item.drop-candidate {
+  box-shadow: inset 0 0 0 1px color-mix(in srgb, var(--accent) 45%, transparent);
+}
+
 .u-nav .file-icon {
   display: block;
   height: 52px;