Icons.display path only handles svg/png, so jpg-backed icons never
rendered. Remove jpg/jpeg: drop from EXT map and magicOk in ingest.js,
narrow FILE regex in sets.js to (svg|png), update the file input
accept attribute in icon_sets_panel.js, and simplify the content-type
ternary in the icon_sets route (jpeg branch was now unreachable).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>