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-attestation.txt

@@ -0,0 +1,34 @@
+==============================================================================
+attestation: DIRECT requested, attestation: none accepted
+==============================================================================
+
+=== Registration ceremony, then authentication ceremony, no browser involved ===
+POST /login (password) -> HTTP 302, Location: http://localhost:8080/
+
+$ POST /webauthn/register/options
+HTTP 200
+{"attestation":"direct","authenticatorSelection":{"residentKey":"required","userVerification":"preferred"},"challenge":"EDPeleI6Jl4Bjc6-cOqnnZqNHCt0P921DI6jsCNvCBQ","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":"OahmMEZ7JKUXyrKH9QxxzqtW7tnuMfUhmnHnmpg80Bc","displayName":"user"}}
+authenticator produced credentialId m9GhJSmVMlSefrRpC7EitQ and a 178-byte CBOR attestation object
+
+$ POST /webauthn/register
+HTTP 200
+{"success":true}
+
+$ GET /diag/credentials
+HTTP 200
+{"principal":"user","principalType":"UsernamePasswordAuthenticationToken","authorities":["FactorGrantedAuthority [authority=FACTOR_PASSWORD, issuedAt=2026-08-25T17:20:10.080515066Z]","ROLE_USER"],"userEntity":{"name":"user","displayName":"user","id":"OahmMEZ7JKUXyrKH9QxxzqtW7tnuMfUhmnHnmpg80Bc"},"credentials":[{"label":"yubikey-on-my-desk","credentialId":"m9GhJSmVMlSefrRpC7EitQ","signatureCount":0,"uvInitialized":true,"backupEligible":true,"backupState":true,"transports":["hybrid","internal"],"attestationObjectBytes":178,"created":"2026-08-25T17:20:10.707040039Z","lastUsed":"2026-08-25T17:20:10.707040039Z"}]}
+logged out, cookie jar emptied
+
+=== Session dropped. Authenticating with the passkey alone ===
+
+$ POST /webauthn/authenticate/options
+HTTP 200
+{"allowCredentials":[],"challenge":"01OJTPvWOBAxxyk3vTq1FFSaVBEqw-_tMMj2FDlFDq8","extensions":{},"rpId":"localhost","timeout":300000,"userVerification":"preferred"}
+
+$ POST /login/webauthn
+HTTP 200
+{"authenticated":true,"redirectUrl":"/"}
+
+$ GET /me
+HTTP 200
+{"name":"user","authenticationType":"WebAuthnAuthentication","authorities":["FactorGrantedAuthority [authority=FACTOR_WEBAUTHN, issuedAt=2026-08-25T17:20:11.002451577Z]","ROLE_USER"]}