feat(客户数据): 添加一键导出功能并集成xlsx库

- 在ProblemRanking组件中添加导出按钮和功能
- 新增导出API接口并修改axios基础URL
- 添加xlsx依赖用于Excel文件生成
- 实现客户数据展平处理和Excel导出逻辑

my-vue-app/package.json

@@ -23,7 +23,8 @@
     "vue": "^3.5.17",
     "vue-chartjs": "^5.3.2",
     "vue-echarts": "^7.0.3",
-    "vue-router": "^4.5.0"
+    "vue-router": "^4.5.0",
+    "xlsx": "^0.18.5"
   },
   "devDependencies": {
     "@tsconfig/node22": "^22.0.1",
@@ -42,4 +43,4 @@
     "vite-plugin-vue-devtools": "^7.7.2",
     "vue-tsc": "^2.2.8"
   }
-}
+}