rename admin-submit-wrap → admin-form-footer across all templates and CSS

- Updated 6 admin templates: add.php, edit.php, login.php, account.php,
  import.php, pages-edit.php — replaced <div class="admin-submit-wrap">
  with <div class="admin-form-footer">
- Updated 8 CSS selectors in admin.css:
  - .admin-form-footer { margin-top/padding-top } (was .admin-submit-wrap)
  - .admin-form > div:not(.admin-form-footer) grid exclusion guard (×3)
  - .admin-login-box .admin-form > div:not(.admin-form-footer) overrides (×2)
  - .admin-login-box .admin-form-footer compact spacing override
- No visual change; purely a semantic rename to a descriptive class name
- Also marked status-badge.php partial and WCAG 1.3.1 badge tasks as
  already-done in todo/02-php-components.md and todo/04-accessibility.md
  (partial + CSS were fully implemented but todo had not been updated)

public/admin/add.php

@@ -96,7 +96,7 @@ function wasSelected($key, $value) {
 
         <?php $name = 'files'; $label = 'Fichiers du TFE :'; $accept = '.pdf,.jpg,.jpeg,.png,.mp4,.zip'; $hint = 'PDF, JPG, PNG, MP4, ZIP. Max 50 MB par fichier.'; $multiple = true; include APP_ROOT . '/templates/partials/form/file-field.php'; ?>
 
-        <div class="admin-submit-wrap">
+        <div class="admin-form-footer">
             <button type="submit" name="go" class="admin-btn">Soumettre</button>
         </div>
     </form>