P0: Replace content JSON-string with sealed PointCommandPayload + record DTOs.
P0: Accept write() boolean return, suppress echo on failure.
P1: Return commandId from POST endpoints, add RESTful GET /{commandId}.
P1: Add driver-online check via EntityStateMapper, PointCommandValidator.
P2: Add DeviceLockManager for per-device serialized command execution.
P3: Add POST /list API with pagination, commandId idempotency support.