[miklb]

Fixes #1195.

create now also uploads images in article/link/note attachments, so to_external_embed finds a blob to use as thumb. They’re kept out of images so they don’t turn the post into an images embed.

These uploads are best effort: if a cited image can’t be fetched, or it’s over the thumb lexicon maxSize, it logs a warning and posts the embed without a thumb, which is what happens today. That needed a max_size kwarg on upload_media. I modeled it on how Bridgy Fed fetches blobs in atproto.py.

Happy to change it if you’d rather these fail loudly, or want the check somewhere else.

Two things I left out. Let me know if you want either:

• Checking the fetched image’s Content-Type against the thumb’s accept
  (image/*).
• Skipping the upload for attachments that become quote posts (at:// and
  bsky.app URLs), where the image is never used.

Tests cover the thumb, a 404, and an oversized image.

I could follow what was happening with the failing on the end result (image not showing up) and was able to trace it back, but to be clear I only half read Python so I leaned on Claude for the rest.

[snarfed]

Thank you @miklb, this is great! I'll make some tweaks and merge soon.

[snarfed]

Done! I'm deploying this to Bridgy classic now...