fix: support userless passkey login

[pando85]

Summary

• Update passless to soft-fido2 0.13.0 so browsers can enumerate multiple discoverable credentials with getNextAssertion.
• Stop advertising alwaysUv in getInfo while preserving notification-based UV support.
• Add E2E regressions for userless discoverable login and multi-credential userless assertions.

Verification

• cargo test -p passless-rs
• cargo test -p passless-rs --test e2e_client test_client_info -- --ignored --exact --test-threads=1 --nocapture
• cargo test -p passless-rs --test e2e_webauthn test_local_userless_discoverable_passkey -- --ignored --exact --test-threads=1 --nocapture
• cargo test -p passless-rs --test e2e_webauthn test_local_userless_multiple_discoverable_credentials -- --ignored --exact --test-threads=1 --nocapture
• cargo test -p passless-rs --test e2e_webauthn test_local_registration_and_authentication -- --ignored --exact --test-threads=1 --nocapture
• cargo clippy --all-targets --all-features -- -D warnings

Manual verification

• Verified GitHub userless passkey login with two stored github.com credentials using passless and soft-fido2 0.13.0.