Root cause: storage.filesystem.maxsize (5GiB) caused Docker Registry to
delete blob data while keeping metadata. Registry then served 200 OK with
correct Content-Length but 0 bytes body. nginx cached these broken responses.
Fixes:
- Remove maxsize from dockerhub/ghcr proxy configs (rely on weekly GC)
- nginx: don't cache 206 responses, require 2 requests before caching
- Wiped corrupted cache on registry VM and fixed corrupted pause container
blobs on node3/node4