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/ca/panel.php

@@ -521,6 +521,15 @@ return [
             'needs_help' => 'Busca gent',
             'needs_help_hint' => 'El mostra a la secció de col·laboració del web.',
         ],
+        'taskstream' => [
+            'section' => 'TaskStream',
+            'section_hint' => 'Un tauler públic a TaskStream, el gestor de tasques del col·lectiu, al teu nom.',
+            'toggle' => 'Crear-lo també a TaskStream',
+            'key' => 'Clau a TaskStream',
+            'key_hint' => 'De 2 a 10 lletres o xifres, començant per lletra. Si la deixes buida, es treu de l\'slug.',
+            'created' => 'Tauler creat a TaskStream: :url',
+            'open' => 'Obrir a TaskStream',
+        ],
         'filters' => ['unpublished' => 'Sense publicar'],
         'actions' => ['publish' => 'Publica'],
     ],