Add passkeys project: WebAuthn ceremonies, a software authenticator and the one-time-token fallback

Fourth Maven project in the repository. Registration and authentication run end to
end with no browser and no hardware key: VirtualAuthenticator emits real CBOR
attestation objects and real ES256 assertion signatures, and tools/PasskeyCeremony.java
drives the live HTTP endpoints with them.

Profiles cover userVerification REQUIRED, DIRECT attestation, a disallowed origin and
JDBC persistence. Eleven doc chapters and twelve captured transcripts under docs/passkeys
and docs/output/pk-*.txt, all regenerated by passkeys/scripts/run-all.sh.

docs/output/pk-step-up.txt

@@ -0,0 +1,41 @@
+==============================================================================
+FactorGrantedAuthority - password, magic link and passkey are not interchangeable
+==============================================================================
+
+=== An endpoint guarded by hasAuthority("FACTOR_WEBAUTHN") ===
+POST /login (password) -> HTTP 302, Location: http://localhost:8080/
+
+$ POST /webauthn/register/options
+HTTP 200
+{"attestation":"none","authenticatorSelection":{"residentKey":"required","userVerification":"preferred"},"challenge":"2LH6xjc9-LwKl-KldFIox5EkCGBVuDXps87yofG4piA","excludeCredentials":[],"extensions":{"credProps":true},"pubKeyCredParams":[{"alg":-8,"type":"public-key"},{"alg":-7,"type":"public-key"},{"alg":-257,"type":"public-key"}],"rp":{"id":"localhost","name":"ankurm passkeys demo"},"timeout":300000,"user":{"name":"user","id":"p6EhVt4x7b3PsL3M94Vuczh2BQyWCSurlu1YBG6lAvs","displayName":"user"}}
+authenticator produced credentialId AkXU5KRzDgeoY4RFXG0mqg and a 178-byte CBOR attestation object
+
+$ POST /webauthn/register
+HTTP 200
+{"success":true}
+
+password session -> GET /passkey-only: HTTP 302, Location: http://localhost:8080/login?factor.type=webauthn&factor.reason=missing
+logged out, cookie jar emptied
+
+=== One-time token: the way in when there is no passkey yet, and the way back ===
+POST /ott/generate -> HTTP 302, Location: http://localhost:8080/login/ott
+token delivered out of band (the handler wrote it to a file): 9ae7d90d-74fe-49ec-9502-fe857fe8972a
+POST /login/ott -> HTTP 302, Location: http://localhost:8080/
+
+$ GET /me
+HTTP 200
+{"name":"user","authenticationType":"OneTimeTokenAuthentication","authorities":["FactorGrantedAuthority [authority=FACTOR_OTT, issuedAt=2026-08-25T17:20:54.745020051Z]","ROLE_USER"]}
+
+=== The same token, a second time ===
+POST /login/ott -> HTTP 302, Location: http://localhost:8080/login?error
+
+one-time-token session -> GET /passkey-only: HTTP 302, Location: http://localhost:8080/login?factor.type=webauthn&factor.reason=missing
+logged out, cookie jar emptied
+
+$ POST /login/webauthn
+HTTP 200
+{"authenticated":true,"redirectUrl":"/"}
+
+$ passkey session -> GET /passkey-only
+HTTP 200
+{"ok":"this endpoint required FACTOR_WEBAUTHN"}