Add EventCompressor static class with Snappy/S2 compress/decompress, threshold-based ShouldCompress, CompressIfBeneficial with stats tracking, and GetCompressionRatio helpers. Port 10 tests covering round-trip, threshold logic, stats (TotalCompressed, BytesSaved, ResetStats). Go reference: server/events.go:2082-2098 compressionType / snappyCompression.