filepond: implement async server-ID upload architecture with nested queue support + PeerTube integration

Replace `storeAsFile:true` with a full async FilePond round-trip pipeline using opaque server-side file IDs.

* Added 4 new PHP endpoints under `/admin/actions/filepond/`:

  * `process.php` — upload/process single file and return opaque `file_id`
  * `revert.php` — delete pending tmp uploads before form submit
  * `load.php` — stream existing files by DB ID for FilePond preload
  * `remove.php` — soft-delete `thesis_files` rows
* `process.php` improvements:

  * accept arbitrary FilePond field names instead of hardcoded `file`
  * support PHP-nested multi-file queue inputs (`queue_file[tfe][]`)
  * explicit unwrapping of nested `$_FILES` structures
  * add `audio/mp3` to audio + `peertube_audio` MIME whitelists
  * immediate upload of `peertube_*` files to PeerTube, returning `peertube:{uuid}` IDs
  * extensive `error_log()` instrumentation for request, CSRF, MIME, upload, and save stages
* `revert.php` now accepts `peertube:` IDs without local cleanup
* `ThesisFileHandler`:

  * add `handleFilePondQueueFiles()` + `handleFilePondSingleFile()`
  * process async uploads from `storage/tmp/filepond/` via opaque `file_id`
  * inline handling of `peertube:{uuid}` IDs with direct `thesis_files` insertion
  * remove obsolete deferred PeerTube queue-processing flow
* `ThesisCreateController` + `ThesisEditController`:

  * gate async path behind `filepond_mode=1`
  * preserve legacy multipart flow as fallback
* `file-upload-filepond.js`:

  * remove `storeAsFile:true`
  * add `buildServerConfig()` for async endpoint wiring
  * fix `syncOrderInput()` to use `serverId`
  * add `onprocessfile` hook
  * add `fileValidateSizeFilterItem` for per-extension size caps
  * preload existing uploads via `data-existing-files` + `server.load`
  * replace static `INPUT_ID_TO_TYPE` map with `data-queue-type`
  * add extensive `console.log()` debugging across upload pipeline stages
* `upload-progress.js`:

  * block form submission while uploads are pending
  * update `collectFileNames()` to read processed FilePond items
* Templates/layout:

  * add `data-queue-type`
  * add `data-existing-files`
  * add global CSRF meta tag outside admin-only context
  * add `filepond_mode` hidden input
  * add CSRF token/meta support for partage pages
  * move website URL field below file upload block
* `.gitignore`: exclude `storage/tmp/` from version control

app/templates/partials/form/form.php

@@ -145,6 +145,7 @@ $checkedFormatsForSiteWeb = $checkedFormatsForSiteWeb ?? [];
 
     <form action="<?= $formAction ?>" method="post" enctype="multipart/form-data" class="admin-form" data-beforeunload-guard data-upload-progress>
         <input type="hidden" name="progress_token" value="<?= bin2hex(random_bytes(8)) ?>">
+        <input type="hidden" name="filepond_mode" value="1">
         <?= $hiddenFields ?>
 
         <?php if (!$adminMode): ?>
@@ -322,6 +323,25 @@ $checkedFormatsForSiteWeb = $checkedFormatsForSiteWeb ?? [];
         $_POST['website_label'] = $existingWebsiteLabel;
         $_POST['admin_mode']    = $adminMode ? '1' : '0';
         $_POST['has_annexes']   = $formData['has_annexes'] ?? null;
+
+        // Build existing-files JSON for FilePond edit mode
+        $existingFilesJsonForTfe = [];
+        if (!empty($currentFiles)) {
+            foreach ($currentFiles as $f) {
+                $ft = $f['file_type'] ?? '';
+                $fp = $f['file_path'] ?? '';
+                // Skip cover (handled separately) and website/peertube (no actual file)
+                if ($ft === 'cover' || str_starts_with($fp, 'http://') || str_starts_with($fp, 'https://') || str_starts_with($fp, 'peertube_ids:')) {
+                    continue;
+                }
+                // Only include files that can be streamed back via load.php
+                $existingFilesJsonForTfe[] = [
+                    'source'  => (string)((int)$f['id']),
+                    'options' => ['type' => 'local'],
+                ];
+            }
+        }
+
         include APP_ROOT . '/public/partage/fichiers-fragment.php';
         $_POST = $_savedPost;
         unset($_savedPost);
@@ -338,6 +358,25 @@ $checkedFormatsForSiteWeb = $checkedFormatsForSiteWeb ?? [];
         $_POST['edit_mode']     = '1';
         $_POST['_cover']        = $currentCover['file_path'] ?? null;
         $_POST['has_annexes']   = $formData['has_annexes'] ?? null;
+
+        // Build existing-files JSON for FilePond edit mode
+        $existingFilesJsonForTfe = [];
+        if (!empty($currentFiles)) {
+            foreach ($currentFiles as $f) {
+                $ft = $f['file_type'] ?? '';
+                $fp = $f['file_path'] ?? '';
+                // Skip cover (handled separately) and website/peertube (no actual file)
+                if ($ft === 'cover' || str_starts_with($fp, 'http://') || str_starts_with($fp, 'https://') || str_starts_with($fp, 'peertube_ids:')) {
+                    continue;
+                }
+                // Only include files that can be streamed back via load.php
+                $existingFilesJsonForTfe[] = [
+                    'source'  => (string)((int)$f['id']),
+                    'options' => ['type' => 'local'],
+                ];
+            }
+        }
+
         include APP_ROOT . '/public/partage/fichiers-fragment.php';
         $_POST = $_savedPost;
         unset($_savedPost);