Image variants were written to the ephemeral release directory
and wiped on every deploy, causing 500 errors with 50s timeouts
as browsers waited for images that could never be served.
- Point image_cache_dir at /data/image_cache in prod
- Add Plug.Static to serve from the persistent volume
- Exclude /image_cache/ from broken URL tracking
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>