fix: locked_year cleared on edit — populate edit dialog field

The openEditDialog JS function didn't populate the locked_year input
in the edit dialog, and the PHP template didn't pass locked_year as an
argument. Any edit to a link (even just changing the name) would clear
the locked academic year to NULL.

- Pass $linkLockedYear as 5th argument to openEditDialog in the template
- Accept and populate edit-locked-year input in the JS handler

app/templates/admin/acces.php

@@ -94,7 +94,7 @@
                                 </button>
                                 <?php endif; ?>
                                 <button type="button" class="admin-icon-btn admin-icon-btn--edit" title="Éditer"
-                                        onclick="event.stopPropagation(); openEditDialog(<?= $link['id'] ?>, <?= htmlspecialchars(json_encode($linkName), ENT_QUOTES) ?>, <?= $hasLinkPassword ? 'true' : 'false' ?>, <?= htmlspecialchars(json_encode($linkExpiresVal), ENT_QUOTES) ?>)">
+                                        onclick="event.stopPropagation(); openEditDialog(<?= $link['id'] ?>, <?= htmlspecialchars(json_encode($linkName), ENT_QUOTES) ?>, <?= $hasLinkPassword ? 'true' : 'false' ?>, <?= htmlspecialchars(json_encode($linkExpiresVal), ENT_QUOTES) ?>, <?= htmlspecialchars(json_encode($linkLockedYear), ENT_QUOTES) ?>)">
                                     <?= icon('pencil-note') ?>
                                 </button>
                                 <form method="post" action="actions/acces-etudiante.php" class="publish-form" onclick="event.stopPropagation()">