feat(plan): 促销计划创建页面

src/views/promotion/plan/index.vue

+<template>
+  <div class="app-container">
+    <div class="container">
+      促销计划
+    </div>
+  </div>
+</template>
+
+<script setup>
+
+</script>
+
+<style scoped
+  lang="scss"></style>
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