fix(server): open image headers non-blocking and step over standalone JPEG markers

Every header read now goes through openMediaFile, so a path swapped for
a FIFO cannot stall the request waiting for a writer. TEM and restart
markers carry no length field and are skipped as two bytes. The read
error names the file.

Co-Authored-By: Claude Code <noreply@anthropic.com>
104ad78637Julius Marminge committed on 9/5/2026, 8:53:31 PMparentc97ccee
4 files changedLine totals unavailable