fix(dispatch): clean up transient library upload from Direct-Print flow (#730)

The "Print" button on a printer card (and drag-drop-onto-card) used
  FileUploadModal to persist the file as a LibraryFile, then dispatched
  through POST /library/files/{id}/print. The LibraryFile row + disk file
  were left behind after every one-off print, polluting File Manager with
  entries the user never asked to save.

  FilePrintRequest.cleanup_library_after_dispatch (default False) opts
  into post-dispatch cleanup. When set, _run_print_library_file stages
  db.delete(lib_file) in the same transaction as archive_print so a
  mid-flight FTP / start_print failure rolls both back cleanly, commits
  together, then unlinks the library disk file + thumbnail after commit
  succeeds. External library files (is_external=True) are never touched.

  Only the Printers-page Direct-Print PrintModal sets the flag. Every
  other api.printLibraryFile caller (File Manager Print, Project Detail
  Print) leaves it unset — their entries are there by user intent.

  Also moves formatPrintName out of PrintersPage.tsx into a new
  utils/printName.ts module — fa1c46d9 (#881) exported it inline so its
  test could import it, tripping react-refresh/only-export-components.

frontend/src/utils/printName.ts

@@ -0,0 +1,23 @@
+/**
+ * Append a plate label to the print name. When `plateLabel` is provided (resolved
+ * by the caller from the linked archive's plate list — see #881 follow-up), it
+ * is used verbatim, including the explicit "Plate 1" case on multi-plate 3MFs.
+ * Falls back to parsing `plate_N.gcode` from the MQTT gcode_file path, and in
+ * that fallback we only show N > 1 because we can't tell from the path alone
+ * whether the 3MF is multi-plate.
+ */
+export function formatPrintName(
+  name: string | null,
+  gcodeFile: string | null | undefined,
+  t: (key: string, fallback: string, opts?: Record<string, unknown>) => string,
+  plateLabel?: string | null,
+): string {
+  if (!name) return '';
+  if (plateLabel) return `${name} — ${plateLabel}`;
+  if (!gcodeFile) return name;
+  const match = gcodeFile.match(/plate_(\d+)\.gcode/);
+  if (match && parseInt(match[1], 10) > 1) {
+    return `${name} — ${t('printers.plateNumber', 'Plate {{number}}', { number: match[1] })}`;
+  }
+  return name;
+}