feat 搭建架构骨架

src/composables/useCountDown.ts

@@ -0,0 +1,32 @@
+import { computed, onScopeDispose, ref } from 'vue'
+
+/** 倒计时（验证码 60s、二维码失效 4:32 等通用） */
+export function useCountDown(defaultSeconds = 60) {
+  const seconds = ref(0)
+  let timer: ReturnType<typeof setInterval> | null = null
+
+  const isCounting = computed(() => seconds.value > 0)
+
+  function start(total: number = defaultSeconds): void {
+    reset()
+    seconds.value = total
+    timer = setInterval(() => {
+      seconds.value -= 1
+      if (seconds.value <= 0) {
+        reset()
+      }
+    }, 1000)
+  }
+
+  function reset(): void {
+    if (timer !== null) {
+      clearInterval(timer)
+      timer = null
+    }
+    seconds.value = 0
+  }
+
+  onScopeDispose(reset)
+
+  return { seconds, isCounting, start, reset }
+}