Improve image quality of PNGs

The PNGs we were generating looked a bit fuzzy, and the text rendering
was a bit off.

This is because we weren’t rendering them at a high enough resolution.
I’m guessing the default was 72dpi. This commit increases the resolution
to 96dpi, which (locally) seems to be enough to give a good-looking
preview.

app/utils.py

@@ -264,7 +264,8 @@ def get_template(
 def png_from_pdf(pdf_endpoint):
     output = BytesIO()
     with Image(
-        blob=pdf_endpoint.get_data()
+        blob=pdf_endpoint.get_data(),
+        resolution=96,
     ) as image:
         with image.convert('png') as converted:
             converted.save(file=output)