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/templates/admin/edit.php

@@ -106,6 +106,26 @@
     // Languages — either from flash repopulation or current thesis data
     $formData['languages'] = $formData['languages'] ?? $currentLanguages ?? [];
 
+    // Compute "other" languages (those not in the predefined checkbox list)
+    $predefinedLangIds = array_column($languages, 'id');
+    $otherLangIds = array_diff($currentLanguages ?? [], $predefinedLangIds);
+    $selectedOtherLanguages = [];
+    if (!empty($otherLangIds)) {
+        $allLangs = Database::getInstance()->getAllLanguages();
+        $allLangMap = [];
+        foreach ($allLangs as $al) {
+            $allLangMap[(int)$al['id']] = $al['name'];
+        }
+        foreach ($otherLangIds as $lid) {
+            $lid = (int)$lid;
+            if (isset($allLangMap[$lid])) {
+                $selectedOtherLanguages[] = $allLangMap[$lid];
+            }
+        }
+        // Sort alphabetically
+        sort($selectedOtherLanguages, SORT_NATURAL | SORT_FLAG_CASE);
+    }
+
     // Tags — either from flash repopulation or current thesis data
     $keywordsStr = $thesis['keywords'] ?? '';
     $currentTags = $keywordsStr !== '' ? array_map('trim', explode(',', $keywordsStr)) : [];