add full-page drag hint overlay for file drop on upload.

frontend/src/components/upload/UploadIntakeControls.vue

@@ -38,6 +38,16 @@
             :metadata-error-count="metadataErrorCount"
             @upload="onUploadFromModal"
         />
+
+        <Teleport to="body">
+            <div v-if="showFileDragOverlay" class="pointer-events-none fixed inset-0 z-70 bg-background/70">
+                <div
+                    class="absolute inset-[5%] flex items-center justify-center rounded-lg border-2 border-dashed border-primary"
+                >
+                    <p class="text-2xl font-medium text-foreground sm:text-3xl">Drop files</p>
+                </div>
+            </div>
+        </Teleport>
     </div>
 </template>
 
@@ -77,19 +87,28 @@ const emit = defineEmits<{
 
 const fileInputRef = ref<HTMLInputElement | null>(null);
 const configureModalOpen = ref(false);
+const fileDragDepth = ref(0);
 
 onMounted(() => {
+    window.addEventListener('dragenter', onWindowDragEnter);
+    window.addEventListener('dragleave', onWindowDragLeave);
     window.addEventListener('dragover', onWindowDragOver);
     window.addEventListener('drop', onWindowDrop);
+    window.addEventListener('dragend', onWindowDragEnd);
     window.addEventListener('paste', onWindowPaste);
 });
 
 onBeforeUnmount(() => {
+    window.removeEventListener('dragenter', onWindowDragEnter);
+    window.removeEventListener('dragleave', onWindowDragLeave);
     window.removeEventListener('dragover', onWindowDragOver);
     window.removeEventListener('drop', onWindowDrop);
+    window.removeEventListener('dragend', onWindowDragEnd);
     window.removeEventListener('paste', onWindowPaste);
 });
 
+const showFileDragOverlay = computed(() => fileDragDepth.value > 0 && !props.disabled);
+
 const maxImageSizeLabel = computed(() => prettyBytes(maxImageBytes, { binary: true, maximumFractionDigits: 1 }));
 
 const emitPicked = (picked: File[]): void => {
@@ -117,15 +136,37 @@ const isFileDrag = (event: DragEvent): boolean => {
     return Boolean(event.dataTransfer?.types.includes('Files'));
 };
 
+const onWindowDragEnter = (event: DragEvent): void => {
+    if (props.disabled || !isFileDrag(event)) {
+        return;
+    }
+
+    fileDragDepth.value += 1;
+};
+
+const onWindowDragLeave = (event: DragEvent): void => {
+    if (!isFileDrag(event)) {
+        return;
+    }
+
+    fileDragDepth.value = Math.max(0, fileDragDepth.value - 1);
+};
+
 const onWindowDragOver = (event: DragEvent): void => {
     if (props.disabled || !isFileDrag(event)) {
         return;
     }
 
     event.preventDefault();
+
+    if (fileDragDepth.value === 0) {
+        fileDragDepth.value = 1;
+    }
 };
 
 const onWindowDrop = (event: DragEvent): void => {
+    resetFileDragDepth();
+
     if (props.disabled) {
         return;
     }
@@ -137,6 +178,10 @@ const onWindowDrop = (event: DragEvent): void => {
     emitPicked(picked);
 };
 
+const onWindowDragEnd = (): void => {
+    resetFileDragDepth();
+};
+
 const isPasswordInputTarget = (target: EventTarget | null): boolean => {
     if (!(target instanceof HTMLElement)) {
         return false;
@@ -175,5 +220,9 @@ const closeConfigureModal = (): void => {
     configureModalOpen.value = false;
 };
 
+const resetFileDragDepth = (): void => {
+    fileDragDepth.value = 0;
+};
+
 defineExpose({ clearInput, closeConfigureModal });
 </script>