feat(attachments): open file picker directly from sidebar button

Clicking the sidebar "Attachments" button (or pressing `f`) now opens
the browser file picker directly, eliminating the redundant two-step
flow of first revealing the section and then clicking upload.

frontend/src/components/tasks/partials/Attachments.vue

@@ -383,6 +383,10 @@ async function setCoverImage(attachment: IAttachment | null) {
 	emit('taskChanged', updatedTask)
 	success({message: t('task.attachment.successfullyChangedCoverImage')})
 }
+
+defineExpose({
+	openFilePicker: () => filesRef.value?.click(),
+})
 </script>
 
 <style lang="scss" scoped>

frontend/src/views/tasks/TaskDetailView.vue

@@ -351,7 +351,7 @@
 						class="content attachments"
 					>
 						<Attachments
-							:ref="e => setFieldRef('attachments', e)"
+							:ref="e => { setFieldRef('attachments', e); attachmentsRef = e as any }"
 							:edit-enabled="canWrite"
 							:task="task"
 							@taskChanged="({coverImageAttachmentId}) => task.coverImageAttachmentId = coverImageAttachmentId"
@@ -499,7 +499,7 @@
 							v-shortcut="'f'"
 							variant="secondary"
 							icon="paperclip"
-							@click="setFieldActive('attachments')"
+							@click="openAttachments()"
 						>
 							{{ $t('task.detail.actions.attachments') }}
 						</XButton>
@@ -793,6 +793,8 @@ async function scrollToHeading() {
 	scrollIntoView(unrefElement(heading))
 }
 
+const attachmentsRef = ref<InstanceType<typeof Attachments> | null>(null)
+
 const taskViewContainer = ref<HTMLElement | null>(null)
 const scrollContainer = ref<HTMLElement | null>(null)
 const contentBottomMarker = ref<HTMLElement | null>(null)
@@ -997,6 +999,17 @@ function setFieldActive(fieldName: keyof typeof activeFields) {
 	})
 }
 
+function openAttachments() {
+	activeFields.attachments = true
+	nextTick(() => {
+		const el = activeFieldElements.attachments
+		if (el) {
+			scrollIntoView(el)
+		}
+		attachmentsRef.value?.openFilePicker()
+	})
+}
+
 async function saveTask(
 	currentTask: ITask | null = null,
 	undoCallback?: () => void,