Refactor NumberFormatter::format() for improved readability

[brtdv]

Summary

• Apply consistent code formatting with multi-line function signature
• Remove unnecessary is_float() conditional check
• Clarify comment explaining locale decimal point usage
• Use consistent double quotes for strings

Problem

The NumberFormatter::format() method had inconsistent formatting and contained an unnecessary is_float() check. The locale's decimal point is always needed when converting numbers to strings, regardless of whether the input is a float or not, because PHP's (string) cast uses the locale's decimal separator.

Solution

• Simplified the decimal point detection by always using localeconv()
• Applied consistent code style (multi-line signatures, double quotes)
• Added a clearer comment explaining why locale detection is necessary