refactor: Update file upload handling and improve audio analysis categorization

Commit notes

This commit modifies the backend to enhance file upload capabilities by increasing the maximum upload size for audio files to 100MB. It also refines the audio analysis process by improving the categorization logic, ensuring more reliable drum type classification based on filename and analysis results. Additionally, the code has been cleaned up for better readability and maintainability, including standardizing string quotes and restructuring function definitions.