feat(app): 添加全局加载组件和CAS单点登录功能

- 在App.vue中引入GlobalLoading组件并挂载到全局
- 新增src/components/GlobalLoading/index.vue组件文件
- 在auth.js中添加AccessUserKey常量和相关存储方法
- 在login.js中添加logincas和outlogcas接口函数
- 在main.js中注册GlobalLoading全局组件
- 修改Navbar.vue实现CAS登出逻辑和跳转处理
- 增加sessionStorage和localStorage清理机制

Signed-off-by: NewName <1048783178@qq.com>

src/components/GlobalLoading/index.vue

@@ -0,0 +1,83 @@
+<template>
+  <div v-if="visible" class="global-loading">
+    <div class="loading-mask">
+      <div class="loading-content">
+        <div class="loading-spinner"></div>
+        <p class="loading-text">{{ text }}</p>
+      </div>
+    </div>
+  </div>
+</template>
+
+<script>
+export default {
+  name: 'GlobalLoading',
+  data() {
+    return {
+      visible: false,
+      text: '加载中...'
+    }
+  },
+  methods: {
+    show(text = '加载中...') {
+      this.text = text
+      this.visible = true
+    },
+    hide() {
+      this.visible = false
+    }
+  }
+}
+</script>
+
+<style scoped>
+.global-loading {
+  position: fixed;
+  top: 0;
+  left: 0;
+  width: 100%;
+  height: 100%;
+  z-index: 9999;
+}
+
+.loading-mask {
+  position: absolute;
+  top: 0;
+  left: 0;
+  width: 100%;
+  height: 100%;
+  background-color: rgba(0, 0, 0, 0.5);
+  display: flex;
+  justify-content: center;
+  align-items: center;
+}
+
+.loading-content {
+  background: white;
+  padding: 20px 30px;
+  border-radius: 8px;
+  text-align: center;
+  box-shadow: 0 2px 12px rgba(0, 0, 0, 0.15);
+}
+
+.loading-spinner {
+  width: 40px;
+  height: 40px;
+  margin: 0 auto 10px;
+  border: 3px solid #f3f3f3;
+  border-top: 3px solid #0f73ee;
+  border-radius: 50%;
+  animation: spin 1s linear infinite;
+}
+
+.loading-text {
+  margin: 0;
+  font-size: 14px;
+  color: #666;
+}
+
+@keyframes spin {
+  0% { transform: rotate(0deg); }
+  100% { transform: rotate(360deg); }
+}
+</style>