GET /api/v1/file?id=<server> created an FM stream on the agent stream
and committed real state change (TaskTypeFM dispatched). With JWT
cookie SameSite=Lax a victim's browser would still send the cookie on
a top-level cross-site GET, so an attacker could trick a logged-in
user into opening an FM session on any of their own servers, consuming
resources and triggering the agent's FM machinery without consent.
Mirror the GHSA-8qhj-4f8c-j8qg fix: move the route to POST. SameSite=
Lax cookies are not sent on cross-site POST. Frontend (admin-frontend)
adjusted in a follow-up commit.
Co-authored-by: cloudcode <cloudcode@users.noreply.github.com>