Move the PDF cross-reference hyperlink logic out of ProjectPrintWindow
into a standalone translation unit so it can be reused (the CLI PDF
export will call it next):
- injectCrossRefLinks(): emits the URI link annotations for a diagram's
cross-references and folio reports. The scene-to-page mapping is passed
in as a PageGeometry (transform + devToPdf + source-rect lookup) so each
caller supplies its own correct geometry, rather than the helper assuming
a QPrinter.
- convertUriToGoTo(): the PDF post-processor, moved verbatim.
ProjectPrintWindow stays a pure caller: it builds its PageGeometry from the
printer page layout exactly as before and calls the helper. No behavioural
change to GUI PDF export; no class-structure changes.
Per review guidance on #483.