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/vite.config.ts

@@ -0,0 +1,12 @@
+import { defineConfig } from 'vite'
+import vue from '@vitejs/plugin-vue'
+import { resolve } from 'path'
+
+export default defineConfig({
+  plugins: [vue()],
+  resolve: {
+    alias: {
+      '@': resolve(__dirname, 'src')
+    }
+  }
+})