feat(config): allow admin/owner to delete branches

- Added DELETE /pos/api/config/branches/<id> that soft-deletes the branch (is_active=false).

- Restricted to owner/admin; main branch cannot be deleted.

- Added 'Eliminar' button in the branches grid for admin/owner.

pos/templates/config.html

@@ -928,7 +928,7 @@
   <script src="/pos/static/js/pos-utils.js?v=33" defer></script>
   <script src="/pos/static/js/sidebar.js" defer></script>
   <script src="/pos/static/js/kiosk.js" defer></script>
-  <script src="/pos/static/js/config.js?v=33" defer></script>
+  <script src="/pos/static/js/config.js?v=34" defer></script>
   <script src="/pos/static/js/sync-engine.js" defer></script>
   <script>if('serviceWorker' in navigator){navigator.serviceWorker.register('/pos/sw.js',{scope:'/pos/'});}</script>
   <script src="/pos/static/js/pwa-install.js" defer></script>