xpi-v4.0.4

Server:

• Output translated PDFs to the original PDF's directory when
  outputToOriginalDir is enabled; fall back to translated/ otherwise
• Register all generated files (translate, crop, compare, crop-compare)
  in _file_registry so /translatedFile/ can serve them regardless
  of output location
• Pass --custom-system-prompt to pdf2zh / pdf2zh_next CLI directly,
  bypassing the config file write path that was silently skipped for
  services without a config_map entry

Plugin:

• Add outputToOriginalDir toggle and customSystemPrompt textarea to
  preferences UI (both engines)
• When outputToOriginalDir is on, link the translated PDF from its
  original location via Zotero.Attachments.linkFromFile instead of
  copying it into Zotero storage
• Replace service-type attachment titles with human-readable labels:
  翻译（lang）, 双语模式（src-tgt）, 双语双栏（src-tgt）, etc.