Page and cover blobs are content-addressed by unguessable, immutable keys,
but /files sent no Cache-Control, so the browser refetched on every reader
open — defeating the whole-chapter and next-chapter preloading (and re-
proxying every byte through the node server in prod). Send
`Cache-Control: public, max-age=31536000, immutable`.
Bump to 0.124.3.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>