Function combine_patterns 

pub fn combine_patterns(
    case_sensitive: &[impl AsRef<str>],
    case_insensitive: &[impl AsRef<str>],
) -> Option<String>

Combine multiple patterns into a single regex string. Case-sensitive patterns are wrapped in (?:...), case-insensitive in (?i:...). This prevents inline flags from leaking between patterns when joined with |. Returns None if no patterns are provided.