fdbb144cd8
Nextcloud app uploads sent application/octet-stream as Content-Type, causing images to not be recognized. Now both WebDAV PUT and chunked upload paths call refine_content_type() which detects via magic bytes, then extension, then falls back to the client header. Also fixes update_file() which previously hardcoded application/octet-stream. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>