feat: add drag-and-drop file upload to Cloud folders

Drag files over the native file browser area to see a drop zone overlay
with dashed orange border. Dropping files triggers the existing upload
handler. Uses debounced dragleave to prevent flicker between children.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

neode-ui/src/views/CloudFolder.vue

@@ -72,7 +72,23 @@
     </div>
 
     <!-- Native File Browser (for FileBrowser-backed sections) -->
-    <div v-else-if="useNativeUI" class="flex-1 min-h-0 flex flex-col">
+    <div
+      v-else-if="useNativeUI"
+      class="flex-1 min-h-0 flex flex-col relative"
+      @dragover.prevent="onDragOver"
+      @dragleave="onDragLeave"
+      @drop.prevent="onDrop"
+    >
+      <!-- Drag-and-drop overlay -->
+      <div v-if="draggingOver" class="cloud-drop-overlay">
+        <div class="cloud-drop-overlay-inner">
+          <svg class="w-12 h-12 text-white/80 mb-3" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+            <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M7 16a4 4 0 01-.88-7.903A5 5 0 1115.9 6L16 6a5 5 0 011 9.9M15 13l-3-3m0 0l-3 3m3-3v12" />
+          </svg>
+          <p class="text-lg font-medium text-white/90">Drop files to upload</p>
+          <p class="text-sm text-white/50">Files will be added to the current folder</p>
+        </div>
+      </div>
       <!-- Upload progress -->
       <div v-if="uploading" class="glass-card p-3 mb-3 flex items-center gap-3">
         <div class="w-5 h-5 border-2 border-white/20 border-t-white/80 rounded-full animate-spin"></div>
@@ -274,6 +290,27 @@ watch(useNativeUI, async (native) => {
 }, { immediate: true })
 
 const uploadError = ref<string | null>(null)
+const draggingOver = ref(false)
+let dragLeaveTimer: ReturnType<typeof setTimeout> | null = null
+
+function onDragOver() {
+  if (dragLeaveTimer) { clearTimeout(dragLeaveTimer); dragLeaveTimer = null }
+  draggingOver.value = true
+}
+
+function onDragLeave() {
+  // Debounce to avoid flicker when dragging between child elements
+  if (dragLeaveTimer) clearTimeout(dragLeaveTimer)
+  dragLeaveTimer = setTimeout(() => { draggingOver.value = false }, 100)
+}
+
+function onDrop(e: DragEvent) {
+  draggingOver.value = false
+  if (dragLeaveTimer) { clearTimeout(dragLeaveTimer); dragLeaveTimer = null }
+  const dt = e.dataTransfer
+  if (!dt?.files?.length) return
+  handleUpload(Array.from(dt.files))
+}
 
 async function handleUpload(files: File[]) {
   uploading.value = true