Add critical rules: always Tailwind, always translate user text

- Strengthen CLAUDE.md rule 8: Tailwind with no exceptions
- Add CLAUDE.md rule 13: all user-visible text must use translation
  functions (Twig: | translate, PHP: t_var(), JS: CmsApi.t_var())
- Add t_var() reference to hooks-and-api.md and css-js-conventions.md
- Update translate entry in quick-reference.md with all 3 contexts

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

docs/css-js-conventions.md

@@ -96,6 +96,12 @@ CmsApi.hook('/hooks/module_id/', { action: 'getData', id: 123 }).then(function(r
 });
 ```
 
+### Traducción en JavaScript
+Todo texto visible al usuario debe usar `CmsApi.t_var()`:
+```js
+CmsApi.t_var('Inicia sesión para guardar favoritos');
+```
+
 ### Cuándo usar Vue 3
 
 Usar Vue 3 CDN cuando la lógica requiera: