compress / decompress helpers for Light Protocol tokens

Added CompressedTokenHelper.compress(...) and .decompress(...) to the z_trade SDK. Light Protocol's ZK Compression charges roughly $0.000004 per compressed account vs $0.002 for a regular SPL token account — a 500× cost reduction once you're moving more than a few hundred accounts. The helper does the boring CPI plumbing: wrap-and-decompose the user's instruction, route through the Light System…