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

im/package.json

@@ -20,6 +20,7 @@
     "js-audio-recorder": "^1.0.6",
     "js-base64": "^2.5.1",
     "nprogress": "^0.2.0",
+    "pinia": "^4.0.3",
     "prismjs": "^1.29.0",
     "qs": "^6.9.4",
     "svg-sprite-loader": "^5.0.0",
@@ -27,8 +28,7 @@
     "vue-cropper": "^1.1.1",
     "vue-prism-editor": "2.0.0-alpha.2",
     "vue-router": "^4.6.4",
-    "vue-virtual-scroller": "^3.0.4",
-    "vuex": "^4.1.0"
+    "vue-virtual-scroller": "^3.0.4"
   },
   "devDependencies": {
     "@vue/cli-plugin-babel": "^5.0.9",
@@ -58,7 +58,9 @@
     "parserOptions": {
       "parser": "babel-eslint"
     },
-    "rules": {}
+    "rules": {
+      "vue/component-api-style": ["warn", ["script-setup"]]
+    }
   },
   "browserslist": [
     "> 1%",