Open a TaskStream board for a project that has none yet

The project form gets «Crear en TaskStream» while the project has no
board, and `taskstream: true` on a PATCH does the same through the API.
A refusal leaves the edit unsaved; a project with a board keeps it, and
`taskstream_key` without the flag is still ignored.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

lang/es/panel.php

@@ -529,6 +529,8 @@ return [
             'key_hint' => 'De 2 a 10 letras o cifras, empezando por letra. Si la dejas vacía, se saca del slug.',
             'created' => 'Tablero creado en TaskStream: :url',
             'open' => 'Abrir en TaskStream',
+            'create' => 'Crear en TaskStream',
+            'create_heading' => 'Abrir un tablero en TaskStream',
         ],
         'filters' => ['unpublished' => 'Sin publicar'],
         'actions' => ['publish' => 'Publicar'],