refactor: Modularize database page into components and composables

- Extract types to types/database.ts
- Create composables: useDatabaseApi, useDataTable, useQueryExecutor
- Create components: DatabaseSidebar, DataTable, FilterBar, SchemaInfo,
  QueryEditor, QueryColumnsBar, DatabaseStats, TablePagination
- Add horizontal scroll to DataTable with sticky checkbox column
- Configure @ path alias in vite and tsconfig
- Reduce DatabasePage.vue from 1548 to 314 lines

frontend/vite.config.ts

@@ -1,10 +1,15 @@
 import { defineConfig } from 'vite'
 import vue from '@vitejs/plugin-vue'
 import { VitePWA } from 'vite-plugin-pwa'
+import { fileURLToPath } from 'url'
+import path from 'path'
+
+const __dirname = path.dirname(fileURLToPath(import.meta.url))
 
 export default defineConfig({
   resolve: {
     alias: {
+      '@': path.resolve(__dirname, 'src'),
       // Habilitar compilación de templates en runtime para componentes dinámicos
       'vue': 'vue/dist/vue.esm-bundler.js'
     }