The community and enterprise bootstrap scripts now generate a dedicated
`server.auth.sessionCookieEncryptionKey` from 32 random bytes for fresh
installations.
The key is Base64-encoded, persisted independently from the datastore
encryption key, and reused from the generated configuration after
restarts.
The community script now also creates `config.yaml` with mode `0600`
before writing it, matching the existing enterprise behavior.
The server already supports the session cookie encryption key, but the
bootstrap scripts left it unset.
This adds defense-in-depth for newly generated deployments while
preserving the existing server-side nonce validation.
Because this only changes newly generated configuration, existing
installations and sessions are unchanged.
A focused regression test checks key presence, decoded length,
separation from the datastore key, YAML placement, and file mode for
both scripts.
It is included in the infrastructure workflow.
