feat: Add database explorer page with SQLite management

- Add /database page with table explorer, query executor and stats
- Implement MCP tools: list_tables, get_table_schema, get_table_data,
  get_database_stats, execute_query
- Add database API endpoints with security (SELECT only)
- Add database icon to toolbar

frontend/src/App.vue

@@ -10,7 +10,7 @@ import { initToolRegistry, activatePageTools, initToolsOnRefresh } from './servi
 const route = useRoute()
 const router = useRouter()
 
-type PageName = 'home' | 'canvas' | 'components' | 'themes' | 'projects' | 'project-canvas'
+type PageName = 'home' | 'canvas' | 'components' | 'themes' | 'projects' | 'project-canvas' | 'database'
 
 onMounted(async () => {
   // Initialize WebMCP connection