Open a TaskStream board from the panel's project form

A "TaskStream" section on the create form (toggle and optional key,
suggested from the slug) opens the board before saving, as the person
signed in, with the Pireon token of their session. A refusal shows on the
key field and a TaskStream outage as a notification; either way nothing is
saved. The created notification carries the link, and the edit page has
an "Open in TaskStream" button.

Documented in the user manual (and its PDF) and the README.

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

lang/es/panel.php

@@ -521,6 +521,15 @@ return [
             'needs_help' => 'Busca gente',
             'needs_help_hint' => 'Lo muestra en la sección de colaboración de la web.',
         ],
+        'taskstream' => [
+            'section' => 'TaskStream',
+            'section_hint' => 'Un tablero público en TaskStream, el gestor de tareas del colectivo, a tu nombre.',
+            'toggle' => 'Crear también en TaskStream',
+            'key' => 'Clave en TaskStream',
+            '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',
+        ],
         'filters' => ['unpublished' => 'Sin publicar'],
         'actions' => ['publish' => 'Publicar'],
     ],