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>

settings.php

@@ -15,7 +15,7 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
     $action = $_POST['action'] ?? '';
 
     if ($action === 'set_modules' && $family_id) {
-        $all = ['calendar', 'budget', 'holidays', 'gifts', 'garage', 'memo'];
+        $all = ['calendar', 'budget', 'holidays', 'gifts', 'garage', 'memo', 'todo'];
         $enabled = array_values(array_filter($all, fn($m) => isset($_POST['mod_' . $m])));
         if (empty($enabled)) {
             $error = "Vous devez garder au moins un module actif.";
@@ -188,6 +188,7 @@ require __DIR__ . '/header.php';
           'gifts'    => ['icon' => '🎁', 'label' => tr('menu_gifts')],
           'garage'   => ['icon' => '🚗', 'label' => tr('menu_garage')],
           'memo'     => ['icon' => '📝', 'label' => tr('menu_memo')],
+          'todo'     => ['icon' => '✅', 'label' => tr('menu_todo')],
       ];
     ?>
     <form method="post">