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/tsconfig.app.json

@@ -3,6 +3,10 @@
   "compilerOptions": {
     "tsBuildInfoFile": "./node_modules/.tmp/tsconfig.app.tsbuildinfo",
     "types": ["vite/client"],
+    "baseUrl": ".",
+    "paths": {
+      "@/*": ["src/*"]
+    },
 
     /* Linting */
     "strict": true,