refactor: 四端完成 Options API → script setup + vuex → pinia 迁移

- buyer(95) / seller(169) / im(53) / manager(280) 共 597 个组件全部从 Options API 转换为 <script setup>
- 四端 vuex 全部移除，状态管理统一迁移至 pinia 4（stores/ 目录）
- util.js 等基础设施去除 vm 首参依赖；全局属性（$Message/$filters 等）在 script 内改为具名导入
- 被外部 ref 访问的公共组件均已补齐 defineExpose（清单见各端 MIGRATION-VUE3.md）
- 各端 eslint 启用 vue/component-api-style 防止新代码回退 Options API
- 四端 yarn build 全部通过；迁移约定与注意事项已更新至各端 MIGRATION-VUE3.md

buyer/package.json

@@ -21,6 +21,7 @@
     "element-plus": "^2.14.1",
     "js-cookie": "^2.2.1",
     "nprogress": "^0.2.0",
+    "pinia": "^4.0.3",
     "psl": "^1.8.0",
     "qs": "^6.9.4",
     "sass": "^1.63.6",
@@ -28,8 +29,7 @@
     "uuid": "^8.3.2",
     "vue": "^3.5.35",
     "vue-qr": "^5.0.3",
-    "vue-router": "^4.6.4",
-    "vuex": "^4.1.0"
+    "vue-router": "^4.6.4"
   },
   "devDependencies": {
     "@vue/cli-plugin-babel": "^5.0.9",
@@ -41,6 +41,7 @@
     "globals": "^17.13.0",
     "less": "^4.2.0",
     "less-loader": "^11.1.4",
+    "vue-eslint-parser": "^10.4.1",
     "webpack": "^5.95.0"
   },
   "browserslist": [