新增角色管理、世界观设定、章节管理和AI工具调用功能

- 角色管理：CRUD API + 卡片网格UI，每个角色约200字描述
- 世界观设定：单篇长文编辑器，建议500字以上
- 章节管理：CRUD + 排序 API，左右分栏编辑器，单章5000字上限
- AI工具调用：支持工具审批流程和结构化工具调用
- 小说详情页新增章节、角色、世界观入口按钮

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/app/main.py

@@ -6,6 +6,9 @@ from fastapi.middleware.cors import CORSMiddleware
 from .database import init_db
 from .routers.novels import router as novels_router
 from .routers.outlines import router as outlines_router
+from .routers.characters import router as characters_router
+from .routers.chapters import router as chapters_router
+from .routers.world_setting import router as world_setting_router
 from .routers.ai_config import router as ai_config_router
 from .routers.chat import router as chat_router
 
@@ -28,6 +31,9 @@ app.add_middleware(
 
 app.include_router(novels_router)
 app.include_router(outlines_router)
+app.include_router(characters_router)
+app.include_router(chapters_router)
+app.include_router(world_setting_router)
 app.include_router(ai_config_router)
 app.include_router(chat_router)