The /favicon.ico route 302-redirected to the uploaded file. Firefox/Chrome
follow that, but Safari does NOT reliably follow a redirect for favicon
requests — it falls back to the HTML <link>, i.e. the bundled picpeak
default. Stream the file bytes directly for local /uploads favicons (with a
path-containment guard); only external URLs and the missing-favicon fallback
still redirect. sendFile sets the content-type from the extension.