Initial public release.

• Core pipeline: SecurityEngine + SecurityLayer interface, fail-fast, order-preserving, framework-agnostic.
• PayloadSizeLayer — configurable request size limit, rejects oversized payloads before any other processing.
• SignatureLayer — real HMAC-SHA256 signature verification (CryptoUtils), bound to request body + timestamp + userId, with clock-skew replay protection.
• ValidationLayer — structural validation and payload sanitization.
• SandboxLayer — dry-run simulation against mock account state.
• RateLimitLayer — sliding-window rate limiting backed by a pluggable StorageAdapter.
• QuantumQuarantineLayer — transparent, rule-based anomaly scoring with persistent known-device/IP history to avoid false positives for returning users.
• AuthorizationLayer — known-user, restricted-action, and per-user limit enforcement.
• LoggingLayer — structured audit logging with a pluggable sink.
• StorageAdapter interface with MemoryStorage (default) and RedisStorage (in-memory-backed until a real client is wired in).
• SecurityConfig for shared, tunable thresholds across layers.
• Full test suite covering signature verification, storage persistence, and payload size limits.