partage: lock Année field to link's locked_year when present

When a student-access share link specifies a locked_year, the Année field
in the student-facing form is now pre-filled with that year and rendered
as disabled+readonly, with a hidden input ensuring the value is submitted.

- renderShareLinkForm() exposes  from ['locked_year']
- fieldset-academic.php checks for : if set, outputs a hidden
  input plus the visible field locked to that value; otherwise falls back
  to the normal editable field

app/templates/partials/form/fieldset-academic.php

@@ -15,15 +15,30 @@ $oldFn           = $oldFn           ?? (function_exists('old') ? 'old' : fn($k,
 $withAutofocusFn = $withAutofocusFn ?? fn($field, $attrs = []) => $attrs;
 $formData        = $formData        ?? [];
 $adminMode       = $adminMode       ?? false;
+$lockedYear      = $lockedYear      ?? null;
 ?>
 <fieldset>
     <legend>Cadre académique</legend>
 
     <?php
-    $name = 'année'; $label = 'Année :'; $value = $oldFn('année'); $required = !$adminMode;
+    $name = 'année'; $label = 'Année :';
+    $required = !$adminMode;
     $type = 'number';
     $placeholder = date('Y');
     $attrs = $withAutofocusFn('année', ['min' => 2000, 'max' => date('Y') + 1]);
+
+    if ($lockedYear !== null):
+        // Link specifies a locked academic year: pre-fill, disable editing.
+        $value = (string)$lockedYear;
+        $attrs['disabled'] = true;
+        $attrs['readonly'] = true;
+        // Include a hidden input so the value is still submitted when the field is disabled.
+        ?>
+        <input type="hidden" name="année" value="<?= htmlspecialchars((string)$lockedYear) ?>">
+        <?php
+    else:
+        $value = $oldFn('année');
+    endif;
     include APP_ROOT . '/templates/partials/form/text-field.php';
     ?>