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/partials/form/form.php

@@ -186,29 +186,45 @@ $checkedFormatsForSiteWeb = $checkedFormatsForSiteWeb ?? [];
             $checked = $formData["languages"] ?? [];
             $required = !$adminMode;
             $hxPost   = $mode === 'partage' ? "/partage/language-autre-fragment" : "/admin/language-autre-fragment.php";
-            $hxTarget = "#language-autre-row";
+            $hxTarget = "#language-autre-required";
             $hxSwap   = "outerHTML";
             include APP_ROOT . "/templates/partials/form/checkbox-list.php";
             unset($hxSwap);
             ?>
             <?php
             $_langAutreRequired = empty($formData["languages"]);
-            $_langAutreValue    = $oldFn("language_autre");
+            // Build selectedLanguages array from form data or current other languages
+            $_selectedOtherLangs = [];
+            if (!empty($formData['language_autre']) && is_array($formData['language_autre'])) {
+                foreach ($formData['language_autre'] as $_l) {
+                    if (is_string($_l) && trim($_l) !== '') {
+                        $_selectedOtherLangs[] = ['name' => trim($_l)];
+                    }
+                }
+            } elseif (!empty($selectedOtherLanguages) && is_array($selectedOtherLanguages)) {
+                $_selectedOtherLangs = array_map(fn($n) => ['name' => $n], $selectedOtherLanguages);
+            } else {
+                $_langRaw = $formData["language_autre"] ?? '';
+                if (is_string($_langRaw) && $_langRaw !== '') {
+                    foreach (array_map('trim', explode(',', $_langRaw)) as $_l) {
+                        if ($_l !== '') {
+                            $_selectedOtherLangs[] = ['name' => $_l];
+                        }
+                    }
+                }
+            }
+            ?>
+            <?php
+            $name = "language_autre";
+            $label = "Autre(s) langue(s) :";
+            $placeholder = "Rechercher une langue…";
+            $hint = "Si votre TFE contient une langue absente de la liste, précisez-la ici.";
+            $selectedLanguages = $_selectedOtherLangs;
+            $required = $_langAutreRequired && !$adminMode;
+            $hxPost = ($mode === 'partage') ? "/partage/language-search-fragment" : "/admin/language-search-fragment.php";
+            include APP_ROOT . "/templates/partials/form/language-search.php";
+            unset($_langAutreRequired, $_selectedOtherLangs, $_langRaw, $_l, $name, $label, $placeholder, $hint, $selectedLanguages, $required, $hxPost);
             ?>
-            <div id="language-autre-row">
-                <div>
-                    <label for="language_autre">Autre(s) langue(s) :<?= $_langAutreRequired ? ' <span class="asterisk">*</span>' : '' ?></label>
-                    <div>
-                        <input type="text"
-                               id="language_autre"
-                               name="language_autre"
-                               value="<?= $_langAutreValue ?>"
-                               <?= (!$adminMode && $_langAutreRequired) ? 'required' : '' ?>>
-                        <small>Si votre TFE contient une langue absente de la liste, précisez-la ici.</small>
-                    </div>
-                </div>
-            </div>
-            <?php unset($_langAutreRequired, $_langAutreValue); ?>
         </fieldset>
 
         <!-- ═══════════════════ Mots-clés ═══════════════════ -->