feat: add use_cropbox parameter to align rasterizer APIs

Added use_cropbox parameter to rasterize_pdf_page hook to allow
choosing between MediaBox and CropBox rendering:

- Default is use_cropbox=False (MediaBox) for consistency with
  Ghostscript's existing behavior
- Ghostscript: passes -dUseCropBox when use_cropbox=True
- pypdfium: calculates crop values to expand from CropBox to MediaBox
  when use_cropbox=False

This aligns both rasterizers to produce the same output dimensions
by default, making the rasterizer choice transparent for page
geometry.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/ocrmypdf/builtin_plugins/ghostscript.py

@@ -129,6 +129,7 @@ def rasterize_pdf_page(
     filter_vector,
     stop_on_soft_error,
     options,
+    use_cropbox,
 ):
     """Rasterize a single page of a PDF file using Ghostscript."""
     # Check if user explicitly requested a different rasterizer
@@ -145,6 +146,7 @@ def rasterize_pdf_page(
         rotation=rotation,
         filter_vector=filter_vector,
         stop_on_error=stop_on_soft_error,
+        use_cropbox=use_cropbox,
     )
     return output_file