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/src/Database.php

@@ -752,6 +752,21 @@ class Database
         return $stmt->fetchAll();
     }
 
+    /**
+     * Return only the predefined / hardcoded languages used as checkboxes
+     * in the form. All other languages go into the "Autre langue" input.
+     */
+    public function getPredefinedLanguages(): array
+    {
+        $stmt = $this->pdo->query(
+            "SELECT id, UPPER(SUBSTR(name,1,1)) || SUBSTR(name,2) as name, created_at
+             FROM languages
+             WHERE LOWER(name) IN ('français', 'anglais', 'néerlandais', 'francais', 'neerlandais')
+             ORDER BY name"
+        );
+        return $stmt->fetchAll();
+    }
+
     // ========================================================================
     // ADMIN LIST METHOD
     // ========================================================================
@@ -1940,17 +1955,6 @@ class Database
     /**
      * Delete every thesis in the database.
      */
-    public function deleteAllTheses(): int
-    {
-        $ids = $this->pdo->query('SELECT id FROM theses')->fetchAll(\PDO::FETCH_COLUMN);
-        if (empty($ids)) {
-            return 0;
-        }
-        $count = count($ids);
-        $this->bulkDeleteTheses($ids);
-        return $count;
-    }
-
     /**
      * Insert a thesis file record.
      * sort_order defaults to (max existing sort_order + 1) for the thesis.