Fix docx/pptx → PDF conversion broken in v2.2 (clean install + recent Microsoft 365)

[mzyqzmd]

Summary

Since v2.2, converting Word/PowerPoint documents to PDF fails.
This PR fixes both root causes so the conversion works again on a
clean install and on current Microsoft 365 builds.

Root cause

v2.2 migrated the Office interop from the Office PIA to NetOffice,
which introduced two independent regressions:

1. Missing dependencies in the installer (clean-install failure)
   Installer/Product.wxs was not updated to ship the NetOffice
   assemblies. On a clean machine the conversion crashes with
   FileNotFoundException / TypeLoadException because
   NetOffice.dll, OfficeApi.dll, WordApi.dll, ExcelApi.dll,
   PowerPointApi.dll, VBIDEApi.dll are missing from the package.

2. ExportAsFixedFormat throws on recent Microsoft 365 (runtime failure)
   The late-bound ExportAsFixedFormat calls throw
   DISP_E_TYPEMISMATCH (0x80020005) on Microsoft 365 builds with
   tightened type libraries, breaking the conversion even when the
   assemblies are present.

Changes

• ConversionJob_Word.cs
  • Replaced ExportAsFixedFormat with
    document.SaveAs(path, WdSaveFormat.wdFormatPDF).
  • Set application.DisplayAlerts = wdAlertsNone so headless
    conversion does not block on format-compatibility dialogs.
• ConversionJob_PowerPoint.cs
  • Replaced ExportAsFixedFormat with
    document.SaveAs(path, PpSaveAsFileType.ppSaveAsPDF, msoFalse).
• Installer/Product.wxs
  • Added the 6 NetOffice assemblies so they deploy on clean installs.

Testing

• Verified Word and PowerPoint conversion produce correct PDFs
  (page count, CJK fonts, embedded images) via the CLI:
  FileConverter.exe --conversion-preset "To Pdf" input.docx
• Verified the installer now bundles the NetOffice DLLs
  (extract via dark.exe -x).

Scope / known follow-up

Excel → PDF still uses ExportAsFixedFormat because Workbook.SaveAs
does not support PDF output; left unchanged. Same M365 regression
may affect Excel and is a known follow-up.