feat: Implement segment update and regeneration features in Audiobook API and frontend

qwen3-tts-backend/schemas/audiobook.py

@@ -89,6 +89,12 @@ class AudiobookSegmentResponse(BaseModel):
     model_config = ConfigDict(from_attributes=True)
 
 
+class AudiobookSegmentUpdate(BaseModel):
+    text: str
+    emo_text: Optional[str] = None
+    emo_alpha: Optional[float] = None
+
+
 class LLMConfigUpdate(BaseModel):
     base_url: str
     api_key: str