feat(board): 支持批量添加与批量删除任务

- 批量添加面板：一行一条，整批共用目标列、优先级、标签与截止日期
- 快速新增支持粘贴多行文本，直接拆成多条任务
- 多选模式支持全选可见任务、整批删除，撤销时连原顺序一起还原
- 批量创建与删除走 store 的批量方法，一次落盘、一次广播
- 补充单元测试与 E2E 用例

src/components/BoardColumn.spec.ts

@@ -214,3 +214,47 @@ describe('BoardColumn 拖拽事件接线', () => {
     expect(options.filter).toBe('button')
   })
 })
+
+describe('BoardColumn 多选模式', () => {
+  function mountSelectable(tasks: Task[], selectedIds: Set<string>) {
+    const pinia = createPinia()
+    setActivePinia(pinia)
+    const store = useTaskStore()
+    store.init({ repository: createMemoryTaskRepository(tasks), crossTab: false })
+
+    const wrapper = mount(BoardColumn, {
+      props: { column: TODO_COLUMN, tasks: store.byColumn.todo, selectable: true, selectedIds },
+      global: { plugins: [pinia] },
+    })
+    return { store, wrapper }
+  }
+
+  it('卡片变为可勾选，selectedIds 决定勾选态', () => {
+    const { wrapper } = mountSelectable(
+      [makeTask({ id: 'task-1' }), makeTask({ id: 'task-2' })],
+      new Set(['task-2']),
+    )
+
+    expect(wrapper.find('[data-task-id="task-1"]').attributes('aria-checked')).toBe('false')
+    expect(wrapper.find('[data-task-id="task-2"]').attributes('aria-checked')).toBe('true')
+  })
+
+  it('点击卡片 emit select 并带上 id', async () => {
+    const { wrapper } = mountSelectable([makeTask({ id: 'task-1' })], new Set())
+
+    await wrapper.find('article').trigger('click')
+
+    expect(wrapper.emitted('select')).toEqual([['task-1']])
+    expect(wrapper.emitted('open')).toBeUndefined()
+  })
+
+  it('多选时禁止拖拽（同列与跨列都不允许）', () => {
+    const { wrapper } = mountSelectable([makeTask()], new Set())
+    const same = wrapper.find('[data-column-id="todo"]').element
+    const other = document.createElement('div')
+
+    const onMove = lastDragOptions().onMove
+    expect(onMove?.({ from: same, to: same }, new Event('move'))).toBe(false)
+    expect(onMove?.({ from: same, to: other }, new Event('move'))).toBe(false)
+  })
+})