SECURITY UPDATE: env-set cross-proxy Digest auth state leak (libcurl)
debian/patches/CVE-2026-8927.patch: detect env-proxy changes and flush
state.proxydigest to prevent stale Digest auth replay across handle reuses
in lib/url.c, lib/urldata.h.
debian/patches/CVE-2026-8927-tests.patch: add test1647 exercising env-set
cross-proxy Digest auth state leak.