🎨 chore(web): apply ESLint and Prettier auto-fixes (baseline)

- Ran: bun run eslint:fix && bun run lint:fix
- Inserted AGPL license header via eslint-plugin-header
- Enforced no-multiple-empty-lines and other lint rules
- Formatted code using Prettier v3 (@so1ve/prettier-config)
- No functional changes; formatting-only baseline across JS/JSX files

web/src/constants/playground.constants.js

@@ -110,4 +110,4 @@ export const ERROR_MESSAGES = {
 export const STORAGE_KEYS = {
   CONFIG: 'playground_config',
   MESSAGES: 'playground_messages',
-}; 
+};