feat: 落地UI动效——表单错误抖动/数字滚动/卡片悬浮

- 新增styles/transitions.css: 错误shake/按钮状态/弹窗过渡/骨架屏淡入(带prefers-reduced-motion)
- 新增CountUp.vue: KPI数字滚动组件(easeOutCubic+千分位+闪烁提示)
- Dashboard: CEO/IT视图摘要卡片接入CountUp
- main.ts引入全局动效

frontend/src/main.ts

@@ -6,6 +6,7 @@ import { createPinia } from 'pinia'
 import App from './App.vue'
 import router from './router'
 import './style.css'
+import './styles/transitions.css'
 
 const app = createApp(App)