Remove base_dir usage for temp_audio_dir to fix incorrect temp file location

[mrickar]

Description:
Previously, base_dir = os.path.abspath(os.path.dirname(__file__)) was joined with temp_audio_dir, causing temporary files to be created inside the installed library package:

self.temp_audio_dir = os.path.join(base_dir, self.temp_audio_dir)

This problem appears when the project is installed via pip (and lives under site-packages), since temporary files are then placed inside the library package directory instead of an external temp directory.

This led to two issues:

1. Temporary files could not be deleted properly since they were stored inside the package directory.
2. The temp_audio_dir: setting in conversation_config.yaml was misleading, because the code automatically prefixed it with base_dir, making the actual storage location different from what was configured.

This PR removes the base_dir usage so that temp_audio_dir correctly reflects the path defined in conversation_config.yaml and ensures temporary files are placed in the intended external directory.

Impact:

• Temporary files are now created in the correct location
• conversation_config.yaml behaves as expected
• Fixes cleanup issues for temporary audio files when the project is installed via pip