refactor: session-based incremental TFE upload via HTMX, drop SortableJS

Replace the client-side FileArray + Sortable drag-to-reorder with a
server-side session-based upload flow:

- New endpoints: /partage/upload-tfe-file, /partage/remove-tfe-file
  (and /admin/ variants) — single-file incremental upload via HTMX
  multipart/form-data with progress bar support
- Session storage: uploaded files go to STORAGE_ROOT/uploads/{session_id}/
  with metadata in $_SESSION['tfe_uploads']
- file-upload-queue.js reduced to single-file previews only (couverture,
  note_intention, annexes thumbnails)
- ThesisFileHandler gains handleTfeFilesFromSession + writeTfeFileFromSrc
  + cleanupSessionUploads for final commit from session temp
- Sortable.min.js removed from all script tags; drag handles and ghost
  CSS removed
- No file_orders[]/file_labels[] hidden field injection needed
- Upload queue survives page refresh (server-owned list)

This eliminates the SortableJS dependency entirely while keeping the
same UX: pick files, see them in a queue, remove individual files.

app/public/assets/js/file-upload-queue.js

@@ -1,11 +1,11 @@
 /**
  * file-upload-queue.js
  *
- * Renders visual file queues for:
- *   1. #tfe-files-input  — multi-file upload with drag-to-reorder (SortableJS)
- *      and per-file label inputs. Injects hidden file_labels[] / file_orders[].
- *   2. input[data-preview] — single-file previews (couverture, note_intention, etc.)
- *   3. #existing-files-sortable — edit-mode sortable list
+ * Provides single-file previews for file inputs with the data-preview attribute
+ * (couverture, note_intention, annexes, etc.).
+ *
+ * The multi-file TFE queue is rendered server-side via HTMX fragments
+ * (upload-tfe-file.php / remove-tfe-file.php).
  *
  * Exposes window.XamxamInitFileUploads() so HTMX fragments can re-bind
  * after swap without a global event listener.
@@ -52,127 +52,7 @@ window.XamxamInitFileUploads = function () {
 		});
 	}
 
-	// ── 1. TFE multi-file queue ────────────────────────────────────────────
-	var picker = document.getElementById("tfe-files-input");
-	var queue = document.getElementById("tfe-file-queue");
-	var empty = document.getElementById("tfe-file-queue-empty");
-	var sortHint = document.getElementById("tfe-file-queue-sort-hint");
-	if (picker && queue) {
-		console.log(
-			"[file-upload-queue] init TFE queue picker=",
-			picker,
-			"multiple=",
-			picker.multiple,
-		);
-		var fileArray = [];
-
-		if (typeof Sortable !== "undefined") {
-			Sortable.create(queue, {
-				animation: 150,
-				handle: ".fq-drag-handle",
-				ghostClass: "fq-ghost",
-				onEnd: function () {
-					var items = queue.querySelectorAll(".fq-item");
-					var newArr = Array.prototype.map.call(items, function (li) {
-						return fileArray[parseInt(li.getAttribute("data-idx"), 10)];
-					});
-					fileArray = newArr;
-					renderQueue();
-				},
-			});
-		}
-
-		picker.onchange = function () {
-			console.log(
-				"[file-upload-queue] onchange fired, files count:",
-				picker.files.length,
-				"names:",
-				Array.from(picker.files).map(function (f) {
-					return f.name;
-				}),
-			);
-			fileArray = fileArray.concat(Array.from(picker.files));
-			console.log(
-				"[file-upload-queue] fileArray after concat, length:",
-				fileArray.length,
-			);
-			picker.value = "";
-			renderQueue();
-		};
-
-		function renderQueue() {
-			queue.innerHTML = "";
-			if (!fileArray.length) {
-				empty.style.display = "";
-				if (sortHint) sortHint.style.display = "none";
-				injectHiddenFields([]);
-				return;
-			}
-			empty.style.display = "none";
-			if (sortHint) sortHint.style.display = "";
-			fileArray.forEach(function (file, idx) {
-				var li = document.createElement("li");
-				li.className = "fq-item";
-				li.setAttribute("data-idx", idx);
-				li.innerHTML =
-					'<span class="fq-drag-handle" title="R\u00e9ordonner">\u2820</span>' +
-					'<span class="fq-icon">' +
-					iconFor(file) +
-					"</span>" +
-					'<span class="fq-info"><span class="fq-name">' +
-					esc(file.name) +
-					"</span>" +
-					'<span class="fq-size">' +
-					humanSize(file.size) +
-					"</span></span>" +
-					'<button type="button" class="admin-btn-remove fq-remove" aria-label="Retirer ' +
-					esc(file.name) +
-					'">&#x2715;</button>';
-				li.querySelector(".fq-remove").onclick = (function (i) {
-					return function () {
-						fileArray.splice(i, 1);
-						renderQueue();
-					};
-				})(idx);
-				queue.appendChild(li);
-			});
-			injectHiddenFields(Array.from(queue.querySelectorAll(".fq-item")));
-		}
-
-		function injectHiddenFields(items) {
-			var form = picker.closest("form");
-			if (!form) return;
-			form
-				.querySelectorAll(".fq-hidden-label, .fq-hidden-order")
-				.forEach(function (el) {
-					el.remove();
-				});
-			items.forEach(function (li, sortedIdx) {
-				var label = li.querySelector(".fq-label");
-				var lInp = document.createElement("input");
-				lInp.type = "hidden";
-				lInp.name = "file_labels[]";
-				lInp.value = label ? label.value : "";
-				lInp.className = "fq-hidden-label";
-				form.appendChild(lInp);
-				var oInp = document.createElement("input");
-				oInp.type = "hidden";
-				oInp.name = "file_orders[]";
-				oInp.value = sortedIdx + 1;
-				oInp.className = "fq-hidden-order";
-				form.appendChild(oInp);
-			});
-		}
-
-		// On submit, refresh hidden fields from current queue state
-		var form = picker.closest("form");
-		if (form)
-			form.addEventListener("submit", function () {
-				injectHiddenFields(Array.from(queue.querySelectorAll(".fq-item")));
-			});
-	}
-
-	// ── 2. Single-file previews (data-preview attribute) ────────────────────
+	// ── Single-file previews (data-preview attribute) ────────────────────
 	document
 		.querySelectorAll('input[type="file"][data-preview]')
 		.forEach(function (input) {
@@ -221,32 +101,6 @@ window.XamxamInitFileUploads = function () {
 				});
 			};
 		});
-
-	// ── 3. Existing-files sortable (edit mode) ──────────────────────────────
-	var sortList = document.getElementById("existing-files-sortable");
-	if (sortList && typeof Sortable !== "undefined") {
-		Sortable.create(sortList, {
-			animation: 150,
-			handle: ".admin-file-drag-handle",
-			ghostClass: "fq-ghost",
-			onEnd: function () {
-				sortList
-					.querySelectorAll('input[name="file_sort_order[]"]')
-					.forEach(function (el) {
-						el.remove();
-					});
-				sortList
-					.querySelectorAll(".admin-file-list-item[data-file-id]")
-					.forEach(function (li) {
-						var inp = document.createElement("input");
-						inp.type = "hidden";
-						inp.name = "file_sort_order[]";
-						inp.value = li.getAttribute("data-file-id");
-						li.prepend(inp);
-					});
-			},
-		});
-	}
 };
 
 // Bootstrap on page load