feat: add file display to forms and recap pages

- Live file preview on all file inputs (file-field partial, edit template):
  thumbnails for images, emoji icons for PDF/video/zip/vtt, filename + size
- New file-preview.js wired via $extraJs in add.php / edit.php and direct
  <script> in partage/index.php; $extraJs support added to head.php
- admin/recapitulatif.php: replace plain table with rich file list — image
  thumbnails linked to media.php, type badges, human-readable size, date
- partage/recapitulatif.php: full rewrite — shows thesis metadata + files
  list with same rich display (no media links for student privacy)
- form.css: new sections for .file-preview-list (live preview) and
  .recap-file-list / .recap-dl / .partage-recap (recap pages)

app/templates/partials/form/file-field.php

@@ -15,6 +15,7 @@ $accept   = $accept   ?? '';
 $hint     = $hint     ?? null;
 $multiple = $multiple ?? false;
 $id       = $id       ?? $name;
+$previewId = 'fp-' . htmlspecialchars($id);
 ?>
 <div>
     <label for="<?= htmlspecialchars($id) ?>"><?= htmlspecialchars($label) ?></label>
@@ -23,11 +24,13 @@ $id       = $id       ?? $name;
                id="<?= htmlspecialchars($id) ?>"
                name="<?= htmlspecialchars($name) ?><?= $multiple ? '[]' : '' ?>"
                <?= $accept   ? 'accept="'   . htmlspecialchars($accept)  . '"' : '' ?>
-               <?= $multiple ? 'multiple' : '' ?>>
+               <?= $multiple ? 'multiple' : '' ?>
+               data-preview="<?= $previewId ?>">
+        <div id="<?= $previewId ?>" class="file-preview-list" aria-live="polite"></div>
         <?php if ($hint): ?>
         <small><?= htmlspecialchars($hint) ?></small>
         <?php endif; ?>
     </div>
 </div>
 <?php
-unset($accept, $hint, $multiple, $id);
+unset($accept, $hint, $multiple, $id, $previewId);