Implement a serializable key-value store

Implement in C++ an in-memory key-value store with: - put(key: string, value: string), get(key) -> optional<string>, erase(key). - serialize() -> vector<uint8_t> that encodes the entire store state. - deserialize(const vector<uint8_t>&) to restore an identical store state. Constraints: - Use only the provided helper byte I/O functions; do not use external libraries for serialization. - Choose a robust binary format (versioned, length-prefixed) that supports arbitrary bytes in keys/values and Unicode. - Ensure correctness for empty store, very large keys/values, duplicate overwrites, and deletions. - Validate input and handle malformed or truncated streams gracefully with clear error signaling. - Time/space complexity should be O(n) in the total serialized data size; support streaming-friendly encoding. - Provide unit tests and explain complexity, trade-offs (e.g., delimiter-escaped text vs. length-prefixed binary), and failure recovery.