Guard no-JS file uploads: disabled filepond_mode by default, server-side fallback

The partage/admin form had a hardcoded filepond_mode=1 hidden input,
so without JavaScript the server always entered the FilePond async
path — which found no hex IDs and silently dropped all files.

Three-layer fix:
1. HTML: filepond_mode input starts disabled with value=0; JS enables
   it and sets value=1 on DOMContentLoaded (and after HTMX swaps).
   Disabled inputs aren't submitted → server gets no filepond_mode
   → naturally falls to legacy  path.
2. JS: enableFilepondMode() called on page load and hx:afterSwap so
   FilePond-enhanced forms always send filepond_mode=1.
3. Server (defense-in-depth): ThesisFileHandler::hasFilePondQueueData()
   scans POST['queue_file'] for 32-char hex IDs; ThesisCreateController
   and ThesisEditController use it alongside filepond_mode, so even if
   the flag somehow arrives without async upload IDs, the  path
   takes over.

app/src/Controllers/ThesisCreateController.php

@@ -198,7 +198,13 @@ class ThesisCreateController
         $folderPath = $objet . '/' . $data['annee'] . '/' . $folderName . '/';
         $filePrefix = $folderName;
 
-        if (!empty($post['filepond_mode'])) {
+        // Determine upload path: FilePond async (JS enabled, hex IDs present)
+        // vs. legacy multipart (no JS, or JS failed).  The hidden filepond_mode
+        // input starts disabled (value=0, not submitted); JS enables it on load.
+        // Defense-in-depth: if filepond_mode=1 but no hex IDs, fall back to $_FILES.
+        $useFilePond = !empty($post['filepond_mode']) && $this->hasFilePondQueueData($post);
+
+        if ($useFilePond) {
             // New path: files already on server via async FilePond uploads
             // Cover and note_intention also go through FilePond async flow
             $this->handleFilePondSingleFile($thesisId, $post, 'cover', $folderPath, $filePrefix);