Add Database page with new connection feature

- Reorganize project structure: move frontend to web/ directory
- Add Database page with connection list (name, type, subtables, status, created, actions)
- Integrate Element Plus for UI components with dark theme support
- Add Quicksand font for rounded UI design
- Configure root package.json to run frontend from web/ directory

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/src/main.ts

@@ -0,0 +1,15 @@
+import { createApp } from 'vue'
+import { createPinia } from 'pinia'
+import ElementPlus from 'element-plus'
+import 'element-plus/dist/index.css'
+import router from './router'
+import './style.css'
+import App from './App.vue'
+
+const app = createApp(App)
+
+app.use(createPinia())
+app.use(router)
+app.use(ElementPlus)
+
+app.mount('#app')