init: 管理会计OS初始代码

包含前后端完整代码：
- 前端：Vue3+Vite+ElementPlus
- 后端：FastAPI+SQLAlchemy
- 模块：驾驶舱/KPI/战略地图/预警/预算/成本/预测/改善行动
- 当前版本：v1.0.0

frontend/src/main.ts

@@ -0,0 +1,26 @@
+import { createApp } from 'vue'
+import ElementPlus from 'element-plus'
+import zhCn from 'element-plus/dist/locale/zh-cn.mjs'
+import * as ElementPlusIconsVue from '@element-plus/icons-vue'
+import { createPinia } from 'pinia'
+import App from './App.vue'
+import router from './router'
+import './style.css'
+
+const app = createApp(App)
+
+const usedIcons = ['Monitor', 'Document', 'TrendCharts', 'WarningFilled', 'Connection', 'User', 'Bell', 'Menu', 'Setting', 'Expand', 'Fold', 'UploadFilled']
+for (const key of usedIcons) {
+  const component = (ElementPlusIconsVue as any)[key]
+  if (component) app.component(key, component)
+}
+
+app.use(ElementPlus, { locale: zhCn })
+app.use(createPinia())
+app.use(router)
+
+// 应用挂载后立即清理可能残留的弹窗遮罩
+app.mount('#app')
+setTimeout(() => {
+  document.querySelectorAll('.el-overlay').forEach(el => el.remove())
+}, 200)