Add helper to convert American height notation to metric

Create a helper to parse and convert American-style height expressions (e.g., 5' 11" or 6ft 2in) into metric (centimeters).

Implement a function (e.g., convert_height_to_cm(value: str) -> float) that:

1. Parses formats like 5'11", 6 ft 2 in, 5ft, etc.
2. Handles edge cases and spacing variations.
3. Add unit tests with common height formats and expected centimeter outputs.

Goal: Standardize height data across datasets by converting US-style height entries to metric units.