Implements device authentication using HMAC-SHA256 signatures with constant-time comparison for security. Includes timestamp-based auth headers with configurable freshness checking (default 5min) and clock skew tolerance.
Moved index.ts to src/server.ts and created stub files for types, db, auth,
and cli modules. Added minimal placeholder for dashboard. Removed generated
README.md in favor of CLAUDE.md and docs/plan.md.
