chore: 将前端移动到 client/ 目录，准备合并为单仓库

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

client/src/utils/helper.ts

@@ -0,0 +1,18 @@
+import { useDateFormat } from "@vueuse/core"
+import { TASK_TYPE } from "./const"
+
+export function parseTime(utc: Date | string, format = "YYYY年M月D日") {
+  const time = useDateFormat(utc, format, { locales: "zh-CN" })
+  return time.value
+}
+
+export function goHome(router: any, type: TASK_TYPE, display: number) {
+  if (type === TASK_TYPE.Tutorial) {
+    router.push({ name: "home-tutorial", params: { display } })
+  } else if (type === TASK_TYPE.Challenge) {
+    if (display) router.push({ name: "home-challenge", params: { display } })
+    else router.push({ name: "home-challenge-list" })
+  } else {
+    router.push({ name: "home" })
+  }
+}