Function load_locale_file 

pub fn load_locale_file(
    locale: &str,
    locales_dir: &Path,
) -> Result<TranslationMap, String>

What: Load a locale YAML file and parse it into a TranslationMap.

Inputs:

• locale: Locale code (e.g., “de-DE”)
• locales_dir: Path to locales directory

Output:

• Result<TranslationMap, String> containing translations or error

Errors

• Returns Err when the locale code is empty or has an invalid format
• Returns Err when the locale file does not exist in the locales directory
• Returns Err when the locale file cannot be read (I/O error)
• Returns Err when the locale file is empty
• Returns Err when the YAML content cannot be parsed

Details:

• Loads file from locales_dir/{locale}.yml
• Parses YAML structure into nested HashMap
• Returns error if file not found or invalid YAML
• Validates locale format before attempting to load