Optimization of audiobook creation functions: Support flexible maintenance of dubbing scripts

This audiobook creation function is optimized to support more flexible fine-tuning of dubbing scripts to solve areas where AI processing is not in place. The specific optimizations are as follows:

• The dubbing script can be modified, deleted, and new script blocks can be added at will
• The role of each dubbing content can be adjusted
• Users can dynamically maintain roles and support adding/deleting roles