fix: resolve partage form submission issues

- Replace mb_strlen/mb_substr/mb_strtolower with strlen/substr/strtolower
  (mbstring extension missing on server, causing fatal error)
- Scope annexes checkbox HTMX swap to #annexes-input-block with hx-select
  (prevents duplicating entire page inside Fichiers fieldset)
- Split format+fichiers response: #format-fichiers-block (stable) and
  #format-extras-block (swappable, inside Fichiers fieldset). Format
  checkboxes use hx-select to extract only the extras, preserving file queue.
- Keep format extras inline in Fichiers fieldset (no sub-fieldsets). Remove
  website legend input (URL only).
- When PeerTube upload disabled, show direct file upload inputs for
  video/audio (name=files[]).
- Add "Glissez-déposez" sort hint below TFE file queue.
- Fix .fq-name overflow with width:0;min-width:100% chain.
- Remove legend placeholder from .fq-item.
- Merge "Récits et expérimentation" AP into "Narration Spéculative".
  Rename PACS to "Pratique de lart - outils critiques, arts et contexte
  simultanés".
- Remove président·e field from jury fieldset, form templates, and
  controller validation. Keep DB column and display logic for existing data.

app/templates/admin/edit.php

@@ -44,11 +44,11 @@
     $juryPromoteursUlb = [];
     $lecteursInternes = [];
     $lecteursExternes = [];
-    $juryPresident    = null;
     foreach ($jury as $jm) {
         if ($jm['role'] === 'president') {
-            $juryPresident = $jm['name'];
-        } elseif ($jm['role'] === 'promoteur') {
+            continue;
+        }
+        if ($jm['role'] === 'promoteur') {
             if (($jm['is_ulb'] ?? 0) == 1) {
                 $juryPromoteursUlb[] = $jm;
             } else {
@@ -69,7 +69,6 @@
     if (!empty($juryPromoteursUlb) && $juryPromoteurUlb === null) {
         $juryPromoteurUlb = $juryPromoteursUlb[0]['name'];
     }
-    $showPresident   = true;
     $showPromoteurUlb = true;
     $promoteurUlbConditional = false;