refactor(msgpack): replace magic numbers with named constants for improved readability

- Define integer boundary constants (MAX_UINT8, MAX_UINT16, MAX_UINT32, MIN_INT8, MIN_INT16, MIN_INT32)
- Add fixed extension type length constants (FIXEXT1_LEN through FIXEXT16_LEN)
- Create timestamp format and bit manipulation constants for encoding and decoding
- Define marker value offsets and masks for msgpack format types
- Replace all hardcoded magic numbers throughout the codebase with their named constant equivalents

Author: jinzhongjia