feat: add iCal calendar subscriptions

frontend/e2e/backup-roundtrip.spec.ts

@@ -8,6 +8,11 @@ function bottomTab(page: Page, name: string) {
   return page.getByRole('navigation', { name: '主要导航' }).getByRole('button', { name, exact: true })
 }
 
+async function openSidebarView(page: Page, name: string) {
+  await page.getByRole('button', { name: /展开菜单|收起菜单/ }).click()
+  await page.locator('.sidebar').getByRole('button', { name, exact: true }).click()
+}
+
 async function csrf(request: APIRequestContext, baseURL: string) {
   const state = await request.storageState()
   return state.cookies.find(cookie => cookie.name === 'dodo_csrf' && baseURL.includes(cookie.domain))?.value
@@ -50,7 +55,7 @@ test('complete ZIP backup preflights and replace-restores task, habit history, c
   expect(countdownResponse.ok()).toBeTruthy()
 
   await page.goto('/')
-  await bottomTab(page, '设置').click()
+  await openSidebarView(page, '设置')
   const downloadPromise = page.waitForEvent('download')
   await page.getByRole('button', { name: '导出 ZIP' }).click()
   const download = await downloadPromise