admin: semantic HTML pass — checkbox fieldset, landmarks, dl/dt, autocomplete, inline styles

checkbox-list.php partial:
- Replace outer <div>/<label> with <div>/<span class="admin-row-label"> + inner
  <fieldset class="admin-checkbox-group"><legend class="sr-only"> to satisfy
  WCAG 1.3.1 (group label for multi-checkbox rows without duplicating visible text)
- Replace <div class="admin-checkbox-list"> with <ul>; each checkbox wrapped in <li>

admin.css:
- Drop .admin-checkbox-list; add .admin-body fieldset.admin-checkbox-group rules
  (border/padding reset so it doesn't inherit jury-fieldset box styling)
- Extend form-row label rule to span.admin-row-label
- .admin-inline-form + .admin-inline-form { margin-top:.35rem } replaces inline style
- .admin-input--inline / .admin-select--inline get width:160px (was inline style)
- .admin-tags-count + table th sizing via :has() replaces th inline styles

login.php: wrap content in <main id="main-content"> (missing landmark)

account.php:
- <div class="admin-account-status"> → <dl>; __label <span> → <dt>
- <div class="admin-danger-zone__description"> → <p>

index.php: <div class="admin-maintenance-bar"> → <aside role="status" aria-label="Statut du site">

add.php / edit.php: autocomplete="name" on author field, autocomplete="email" on
contact field (WCAG 1.3.5 / input purpose)

tags.php: all inline style= attributes removed (width, text-align, margin-top,
display:inline); all moved to CSS classes

public/admin/edit.php

@@ -70,8 +70,8 @@ try {
         <input type="hidden" name="csrf_token" value="<?= htmlspecialchars($_SESSION['csrf_token']) ?>">
         <input type="hidden" name="thesis_id"  value="<?= $thesisId ?>">
 
-        <?php $name = 'auteurice'; $label = 'Auteur·ice(s) :'; $value = htmlspecialchars($thesis['authors']); $required = true; include APP_ROOT . '/templates/partials/form/text-field.php'; ?>
-        <?php $name = 'mail';      $label = 'Contact :';        $value = '';                                   include APP_ROOT . '/templates/partials/form/text-field.php'; ?>
+        <?php $name = 'auteurice'; $label = 'Auteur·ice(s) :'; $value = htmlspecialchars($thesis['authors']); $required = true; $attrs = ['autocomplete' => 'name'];  include APP_ROOT . '/templates/partials/form/text-field.php'; ?>
+        <?php $name = 'mail';      $label = 'Contact :';        $value = '';                                   $attrs = ['autocomplete' => 'email']; include APP_ROOT . '/templates/partials/form/text-field.php'; ?>
 
         <?php
             $name  = 'année'; $label = 'Année :'; $value = htmlspecialchars((string)$thesis['year']); $required = true;