fix: fenêtres fantômes PyInstaller — désactiver ProcessPoolExecutor en mode frozen

ProcessPoolExecutor relançait l'exe pour chaque sous-processus de
rastérisation sous PyInstaller --onefile, créant une fenêtre GUI par page.
En mode frozen, la rastérisation est maintenant séquentielle.

Aussi: remplacement du mutex Windows par un file lock (msvcrt.locking)
plus fiable pour la protection anti-multi-instance.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

anonymizer_core_refactored_onnx.py

@@ -3583,15 +3583,20 @@ def redact_pdf_raster(original_pdf: Path, audit: List[PiiHit], out_pdf: Path, dp
         image_rects_by_page[pno] = img_rects
     doc.close()  # fermer AVANT le fork
 
-    n_workers = min(n_pages, os.cpu_count() or 4)
     tasks = [
         (str(original_pdf), pno, rects_as_tuples.get(pno, []), dpi, ogc_label, jpeg_quality,
          image_rects_by_page.get(pno, []))
         for pno in range(n_pages)
     ]
 
-    with ProcessPoolExecutor(max_workers=n_workers) as pool:
-        results = sorted(pool.map(_rasterize_page, tasks), key=lambda x: x[0])
+    # Mode frozen (PyInstaller --onefile) : ProcessPoolExecutor relance l'exe
+    # et ouvre des fenêtres GUI fantômes → séquentiel obligatoire
+    if getattr(sys, 'frozen', False) or n_pages <= 2:
+        results = sorted([_rasterize_page(t) for t in tasks], key=lambda x: x[0])
+    else:
+        n_workers = min(n_pages, os.cpu_count() or 4)
+        with ProcessPoolExecutor(max_workers=n_workers) as pool:
+            results = sorted(pool.map(_rasterize_page, tasks), key=lambda x: x[0])
 
     # Assemblage final (séquentiel, rapide)
     out = fitz.open()