Title: Refactor: Improve error handling and remove unused parameter in main.py

Description:

This pull request introduces two refactoring changes to main.py aimed at improving code clarity and maintainability.

1. Use Specific Exception for File Not Found:
   The code previously raised a general IOError when a file was not found. This has been updated to raise the more specific FileNotFoundError. This change provides clearer error information to callers and allows for more precise error handling.

   Before (approx. line 319):

   if raise_error_if_not_found:
       raise IOError("File not found")
   return ""

   After:

   if raise_error_if_not_found:
       raise FileNotFoundError("File not found")
   return ""

This looks good to me but I would like to update the test test_find_dotenv_no_file_raise to reflect this change and squash the commits before rebasing and merging to clean up the git history. It looks like I can't do it myself in this PR, so I might do it in another PR if necessary.