Add Todo module: SPA task manager with lists, priorities and due dates

- New todo.php SPA page with sidebar (smart views + user lists)
- modules/todo/api.php: REST API for lists and todos (CRUD, filters, stats)
- modules/todo/assets/todo.js: frontend (quick add, toggle done, modals)
- modules/todo/assets/todo.css: full light/dark theme styles
- pf_todo_lists + pf_todos tables added to schema_family.sql
- Integrated in header nav, home page cards, settings module list
- Translations added in fr/en/ca

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

includes/lang/fr.php

@@ -96,6 +96,9 @@ return [
     'mod_memo_name'      => 'Notes',
     'mod_memo_desc'      => 'Vos mémos, recettes, instructions et infos diverses avec Markdown et pièces jointes.',
     'menu_memo'          => 'Notes',
+    'mod_todo_name'      => 'Todo',
+    'mod_todo_desc'      => 'Gérez vos tâches, listes de courses et rappels en famille.',
+    'menu_todo'          => 'Todo',
     'cta_open'           => 'Ouvrir',
     'cta_explore'        => 'Explorer',
     'cta_view_lists'     => 'Voir les listes',