This routes external downloads used by avatar sync through SafeFetch. It closes the SSRF exposure from raw Down.download paths, preserves provider-specific auth and header flows, and adds regression coverage
for blocked internal URLs plus authenticated downloads.
Fixes # (issue): [CW-6931](https://linear.app/chatwoot/issue/CW-6931/avatarwidget-url-ssrf-downdownload-unprotected-unauth)
