feat: add continue script functionality for AI-generated audiobook projects

qwen3-tts-backend/core/llm_service.py

@@ -323,6 +323,42 @@ class LLMService:
             system_prompt, user_message, on_token=on_token, max_tokens=4096, usage_callback=usage_callback
         )
 
+    async def generate_additional_chapter_outline(
+        self,
+        genre: str,
+        subgenre: str,
+        premise: str,
+        style: str,
+        existing_chapters: list[Dict],
+        additional_chapters: int,
+        characters: list[Dict],
+        usage_callback: Optional[Callable[[int, int], None]] = None,
+    ) -> list[Dict]:
+        system_prompt = (
+            "你是一个专业的故事创作助手。请根据已有章节大纲，续写新的章节大纲。\n"
+            "每章包含章节索引（从给定起始索引开始）、标题和简介。\n"
+            "新章节必须与已有章节剧情连贯，情节有所推进。\n"
+            "只输出JSON，格式如下，不要有其他文字：\n"
+            '{"chapters": [{"index": N, "title": "标题", "summary": "章节内容简介，2-3句话"}, ...]}'
+        )
+        genre_label = f"{genre}{'/' + subgenre if subgenre else ''}"
+        char_names = [c.get("name", "") for c in characters if c.get("name") not in ("narrator", "旁白")]
+        start_index = len(existing_chapters)
+        existing_summary = "\n".join(
+            f"第{ch.get('index', i) + 1}章「{ch.get('title', '')}」：{ch.get('summary', '')}"
+            for i, ch in enumerate(existing_chapters)
+        )
+        user_message = (
+            f"故事类型：{genre_label}\n"
+            + (f"风格：{style}\n" if style else "")
+            + f"故事简介：{premise}\n"
+            f"主要角色：{', '.join(char_names)}\n\n"
+            f"已有章节大纲（共{len(existing_chapters)}章）：\n{existing_summary}\n\n"
+            f"请从第{start_index}章（索引{start_index}）开始，续写{additional_chapters}章大纲，剧情要承接上文。"
+        )
+        result = await self.stream_chat_json(system_prompt, user_message, max_tokens=4096, usage_callback=usage_callback)
+        return result.get("chapters", [])
+
     async def parse_chapter_segments(self, chapter_text: str, character_names: list[str], on_token=None, usage_callback: Optional[Callable[[int, int], None]] = None) -> list[Dict]:
         names_str = "、".join(character_names)
         system_prompt = (