Add Prettier for TypeScript formatting

- Install prettier
- Configure .prettierrc.json and .prettierignore
- Add npm scripts: format, format:check
- Add Makefile target: format-frontend
- Format all frontend files

frontend/playwright.config.ts

@@ -15,4 +15,3 @@ export default defineConfig({
     baseURL: "http://localhost:3000",
   },
 });
-