Add language-search component for Autre Langue input + active search in lists

Mirrors the mots-clé tag-search system: dropdown suggestions from
existing languages via HTMX, pill display with bin-icon remove buttons,
'Créer' option for new languages. Replaces the plain text input.

- New partial: templates/partials/form/language-search.php
- New fragment: public/partage/language-search-fragment.php
- Admin wrapper: public/admin/language-search-fragment.php
- Updated language-autre-fragment to return just the required asterisk indicator
- Updated both controllers to handle language_autre as array (pill-based)
  with backward-compatible string path
- Updated edit form to compute selectedOtherLanguages from DB
- Registered new route in partage/index.php
- Fix CSV importer: split comma-separated language column into individual entries
- Add htmx active search to admin index, title line-clamp, predefined languages only in checkboxes
- Admin index: filter form now uses htmx triggers (input delay:300ms on search,
  change on selects) to actively search without page reload
- Sort links include hx-push-url for back-button support
- Added loading indicator bar (.admin-search-indicator)
- Title column: line-clamp at 2 lines with overflow hidden, native title attr
  tooltip for full text
- Language checkboxes now show only 3 predefined languages (Français, Anglais,
  Néerlandais); all others go via the Autre langue search component
- Added Database::getPredefinedLanguages() and excluded predefined from
  language-search-fragment suggestions
- Included hidden sort/dir inputs in table-wrap so sort state preserved across
  filter changes
- Fix language-search: block 'Créer' for predefined languages in dropdown
  The 'Créer' option in the language-search dropdown now also checks against the
  predefined set (français, anglais, néerlandais) to avoid offering creation of
  languages that already exist as checkboxes.

app/public/admin/actions/delete.php

@@ -16,20 +16,14 @@ if (!isset($_POST['csrf_token'], $_SESSION['csrf_token'])
     exit;
 }
 
-$isBulk      = !empty($_POST['bulk']);
-$isDeleteAll = !empty($_POST['delete_all']);
+$isBulk = !empty($_POST['bulk']);
 
 try {
     $db = new Database();
 
     $logger = AdminLogger::make();
 
-    if ($isDeleteAll) {
-        $count = $db->deleteAllTheses();
-        $logger->logDeleteAllTheses($count);
-        App::flash('success', "$count TFE(s) supprimé(s) avec succès.");
-
-    } elseif ($isBulk) {
+    if ($isBulk) {
         $ids = array_filter(array_map('intval', $_POST['selected_theses'] ?? []), fn($id) => $id > 0);
 
         if (empty($ids)) {