refactor: rename "folder" to "package" throughout codebase

- Rename CSS files: _card-folder.scss → card-package
- Rename template files: _folder.scss → package
- Update all CSS class names and selectors
- Delete old folder blueprints and templates
- Add new package blueprints with improved structure
- Update investigation-summary template and blueprint
- Add "Dossiers" menu item in panel configuration
- Improve package blueprint with linkedContent field

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

site/templates/folders.php

@@ -1,59 +0,0 @@
-<?php snippet('header') ?>
-<main>
-
-<header class="page__header">
-
-    <h2 class="page__title"><?= $page->title() ?></h2>
-
-    <?php if ($page->chapo()->isNotEmpty()): ?>
-    <div class="description-medium">
-        <p><?= $page->chapo() ?></p>
-    </div>
-    <?php endif ?>
-</header>
-
-<section class="container-cards">
-
-
-
-<?php foreach ($page->children()->listed() as $folder): ?>
-<article class="card--folder">
-
-    <?php if ($cover = $folder->cover()->toFile()): ?>
-    <figure>
-        <img src="<?= $cover->url() ?>" alt="<?= $folder->title()->esc() ?>">
-    </figure>
-    <?php endif ?>
-
-    
-
-    <div class="content">
-        <h4 class="title"><a href="<?= $folder->url() ?>"><span class="icon"><?= svg('assets/icons/folder.svg') ?></span><?= $folder->title()->esc() ?></a></h4>
-
-        <?php if ($folder->description()->isNotEmpty()): ?>
-        <p class="short"><?= $folder->description()->excerpt(200) ?></p>
-        <?php endif ?>
-
-        <?php
-        // Compter les enquêtes associées à ce dossier
-        $investigationsCount = site()->find('enquetes')->children()->listed()->filter(function($investigation) use ($folder) {
-            return $investigation->folder()->value() === $folder->slug();
-        })->count();
-        ?>
-
-            <ul>
-                <?php if ($investigationsCount > 0): ?>
-                    <li><?= $investigationsCount ?> enquête<?= $investigationsCount > 1 ? 's' : '' ?></li>
-                <?php endif ?>
-                    <li>8 impacts</li>
-                </ul>
-
-    </div>
-    <button class="btn--go-to"><a href="#" target="_blank"><?= svg('assets/icons/arrow-left.svg') ?></a></button>
-    <a class="link-block" href="<?= $folder->url() ?>"></a>
-</article>
-<?php endforeach ?>
-
-</section>
-</main>
-<?php snippet('footer') ?>