GET /api/me now carries the profile picture URL when the provider
supplies an absolute http(s) one; the SPA shows it in the lobby navbar
and draws a deterministic identicon from the sub otherwise, falling back
to the identicon when the image fails to load.
The identicon is a 5x5 mirrored grid seeded by an inline FNV-1a hash so
it stays stable across Rust versions and is unit-testable on the host.
The dev mock IdP hands alice and bob a picture claim.
woggioni
532cb16f94