Replace custom file-upload-queue.js with FilePond

- Delete file-upload-queue.js (495 lines of custom queue logic)
- Delete sortable.min.js dependency
- Add file-upload-filepond.js: thin wrapper that upgrades .tfe-file-picker
  inputs to FilePond instances with storeAsFile:true for native multipart
  form submission (no form-submit interception needed)
- Update fichiers-fragment.php: replace queue container <ul> elements
  and empty-state <p> with bare <input> elements that FilePond upgrades;
  change name attributes to queue_file[tfe][] etc. for PHP compatibility
- Update add.php, edit.php, partage/index.php: swap JS/CSS refs
- Clean up form.css: remove .fq-* and .tfe-file-queue custom styles,
  add FilePond theme overrides matching xamxam design tokens
- Update dead-code fieldset-files.php for consistency

Server-side stays unchanged: PHP receives ['queue_file']['tfe'][]
exactly as before through native multipart submission.

app/public/assets/css/form.css

@@ -532,7 +532,7 @@
   color: var(--danger, #c1121f);
 }
 
-/* ── TFE file upload queue (.tfe-file-queue) ────────────────────────────── */
+/* ── TFE file upload (FilePond) ────────────────────────────────────────── */
 
 .admin-files-fieldgroup {
   display: flex;
@@ -540,124 +540,46 @@
   gap: var(--space-3xs);
 }
 
-.tfe-file-picker {
-  font-size: var(--step--1);
-  background: transparent;
+/* FilePond overrides to match xamxam theme */
+.filepond--root {
+  font-family: var(--font-body, inherit);
+  margin-bottom: 0;
+}
+
+.filepond--panel-root {
+  background: var(--bg-secondary);
   border: 1px dashed var(--border-primary);
-  padding: var(--space-3xs) var(--space-2xs);
-  border-radius: var(--radius);
-  cursor: pointer;
-  font-family: inherit;
-  width: 100%;
 }
 
-.tfe-file-picker:hover {
-  border-color: var(--accent-primary);
+.filepond--drop-label {
+  color: var(--text-secondary);
+  font-size: var(--step--1);
 }
 
-/* New-file queue items */
-.tfe-file-queue {
-  list-style: none;
-  margin: var(--space-2xs) 0 0;
-  padding: 0;
-  display: flex;
-  flex-direction: column;
-  gap: var(--space-2xs);
-  min-width: 0;
+.filepond--label-action {
+  color: var(--accent-primary);
+  text-decoration: underline;
 }
 
-.tfe-queue-empty {
-  font-size: var(--step--2);
-  color: var(--text-tertiary);
-  margin: var(--space-3xs) 0 0;
-}
-
-.tfe-file-queue:not(:empty) + .tfe-queue-empty {
-  display: none;
-}
-
-.fq-item {
-  display: flex;
-  align-items: center;
-  gap: var(--space-xs);
-  padding: var(--space-3xs) var(--space-xs);
+.filepond--item-panel {
   background: var(--bg-secondary);
   border: 1px solid var(--border-primary);
-  border-radius: var(--radius);
-  min-width: 0;
 }
 
-.fq-icon {
-  font-size: 1.3rem;
-  line-height: 1;
-  flex-shrink: 0;
-  width: 2rem;
-  text-align: center;
-}
-
-.fq-info {
-  display: flex;
-  flex-direction: column;
-  gap: var(--space-3xs);
-  flex: 1;
-  min-width: 0;
-}
-
-.fq-name {
-  font-size: var(--step--1);
-  font-weight: 500;
-  white-space: nowrap;
-  overflow: hidden;
-  text-overflow: ellipsis;
-  width: 0;
-  min-width: 100%;
-}
-
-.fq-size {
-  font-size: var(--step--2);
-  color: var(--text-tertiary);
-}
-
-.fq-label,
-.admin-file-label-input {
-  font-size: var(--step--2);
-  font-family: inherit;
-  background: transparent;
-  border: none;
-  border-bottom: 1px solid var(--border-primary);
-  padding: 2px 0;
-  width: 100%;
+.filepond--file-info-main {
   color: var(--text-primary);
-  border-radius: 0;
 }
 
-.fq-label:focus,
-.admin-file-label-input:focus {
-  outline: none;
-  border-bottom-color: var(--accent-primary);
-}
-
-.fq-remove {
-  flex-shrink: 0;
-}
-
-.fq-drag-handle {
-  flex-shrink: 0;
-  cursor: grab;
+.filepond--file-info-sub {
   color: var(--text-tertiary);
-  font-size: 1.1rem;
-  line-height: 1;
-  padding: 0 var(--space-3xs);
-  user-select: none;
-  touch-action: none;
 }
 
-.fq-drag-handle:active {
-  cursor: grabbing;
+.filepond--file-action-button {
+  color: var(--text-secondary);
 }
 
-.fq-container {
-  /* wrapper div emitted by renderQueueFragment */
+.filepond--file-action-button:hover {
+  color: var(--error);
 }
 
 /* ── Existing-files list (edit form) ─────────────────────────────────────── */