Cache successful Basic Auth verifications for 30s using blake3(username:password)
as cache key. This eliminates repeated Argon2id computation (~3-5ms CPU + 64MiB
RAM) and 3 PostgreSQL round-trips per DAV request from the same client.
- Add moka::future::Cache<[u8;32], CachedBasicAuthResult> field
- Cache hits return in ~200ns vs ~5ms (25,000x improvement)
- Failed verifications are never cached (brute-force protection intact)
- revoke() invalidates all cached entries for the affected user
- ~1.6MB max memory footprint (10,000 entries)