This adds native, clickable hyperlinks to PDF exports: cross-references jump

directly to the related component on its folio, framing the target element.

When a project is exported to PDF, every cross-reference becomes an internal
link. Four kinds are covered:

- **Master → contact**: the contact list on a coil/relay (`CrossRefItem`)
- **Folio report → report**: report element labels (`DynamicElementTextItem`)
- **Slave → master**: the `(folio-position)` reference shown on a slave
  (both standalone `DynamicElementTextItem` and grouped `ElementTextItemGroup`)

Clicking a link navigates **inside** the open document (no new viewer
instance) and zooms to frame the target element.

1. **Injection** (`printDiagram`, only when the paint engine is a `QPdfEngine`):
   link rectangles are added with `QPdfEngine::drawHyperlink()`. The scene→page
   mapping is rebuilt to match exactly what `QGraphicsScene::render()` does
   (top-left anchored, `KeepAspectRatio`, **no centering**), and rectangles are
   passed in device pixels — `pageMatrix()` already applies the 72/resolution
   scale and Y-flip internally.

2. Each link URL encodes the target page and the target element's rectangle, in
   PDF points on its own page: `#page=N&fitr=L_B_R_T`.

3. **Post-processing** (`pdfConvertUriToGoTo`, run after the painter is closed):
   the `/S /URI` annotations are rewritten to native `/S /GoTo` actions with a
   `/D [pageObj 0 R /FitR L B R T]` destination, and the xref table is rebuilt.
   Pages are enumerated from the `/Pages /Kids` tree (reliable), not by scanning
   for `/Type /Page` in raw bytes.

- `sources/print/projectprintwindow.{cpp,h}` — injection + post-processing
- `sources/qetgraphicsitem/crossrefitem.{cpp,h}` — `hoveredContactsMap()` accessor; store text rect for hit area
- `sources/qetgraphicsitem/dynamicelementtextitem.h` — `slaveXrefItem()` / `masterElement()` accessors
- `sources/qetgraphicsitem/elementtextitemgroup.h` — `slaveXrefItem()` accessor
- `qelectrotech.pro`, `cmake/qet_compilation_vars.cmake` — enable Qt gui-private headers (`<private/qpdf_p.h>`)

- **Fit-to-page mode only.** Links are not injected in tiled mode (multiple
  pages per folio), which would require a per-tile transform.
- Uses Qt private API (`QPdfEngine::drawHyperlink`), stable since Qt 4 but not
  part of the public API; the build links against `gui-private`.
- Page-tree enumeration assumes the flat `/Kids` array Qt produces (no nested
  page trees).
- The frame zoom is controlled by two constants in `destRectPdf` (`pad`,
  `minSide`) and can be tuned.
- Tested on Qt5; the `/Kids` parsing and `pageMatrix` behaviour are identical on
  Qt6.

qelectrotech.pro

@@ -230,7 +230,11 @@ RESOURCES += qelectrotech.qrc
 TRANSLATIONS += lang/*.ts
 
 # Modules Qt utilises par l'application
-QT += xml svg network sql widgets printsupport concurrent KWidgetsAddons KCoreAddons
+QT += xml svg network sql widgets printsupport concurrent KWidgetsAddons KCoreAddons gui-private
+
+# Private Qt GUI headers (needed for QPdfEngine::drawHyperlink)
+# gui-private should add this automatically, but some distros need it explicit
+INCLUDEPATH += $$[QT_INSTALL_HEADERS]/QtGui/$$[QT_VERSION]/QtGui
 
 # UI DESIGNER FILES AND GENERATION SOURCES FILES
 FORMS += $$files(sources/richtext/*.ui) \