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/routers/characters.py

@@ -0,0 +1,103 @@
+from datetime import datetime, timezone
+
+from fastapi import APIRouter, Depends, HTTPException
+from sqlmodel import Session, select, func
+
+from ..database import get_session
+from ..models import Novel, Character
+from ..schemas import (
+    CharacterCreate,
+    CharacterUpdate,
+    CharacterRead,
+    CharacterList,
+)
+
+router = APIRouter(prefix="/api/novels/{novel_id}/characters", tags=["characters"])
+
+
+def _get_novel_or_404(novel_id: int, session: Session) -> Novel:
+    novel = session.get(Novel, novel_id)
+    if not novel:
+        raise HTTPException(status_code=404, detail="小说不存在")
+    return novel
+
+
+def _get_character_or_404(
+    character_id: int, novel_id: int, session: Session
+) -> Character:
+    character = session.get(Character, character_id)
+    if not character or character.novel_id != novel_id:
+        raise HTTPException(status_code=404, detail="角色不存在")
+    return character
+
+
+@router.get("", response_model=CharacterList)
+def list_characters(
+    novel_id: int,
+    session: Session = Depends(get_session),
+):
+    _get_novel_or_404(novel_id, session)
+    total = session.exec(
+        select(func.count(Character.id)).where(Character.novel_id == novel_id)
+    ).one()
+    items = session.exec(
+        select(Character)
+        .where(Character.novel_id == novel_id)
+        .order_by(Character.created_at)
+    ).all()
+    return CharacterList(
+        items=[CharacterRead.model_validate(c, from_attributes=True) for c in items],
+        total=total,
+    )
+
+
+@router.post("", response_model=CharacterRead, status_code=201)
+def create_character(
+    novel_id: int,
+    data: CharacterCreate,
+    session: Session = Depends(get_session),
+):
+    _get_novel_or_404(novel_id, session)
+    character = Character(novel_id=novel_id, **data.model_dump())
+    session.add(character)
+    session.commit()
+    session.refresh(character)
+    return character
+
+
+@router.get("/{character_id}", response_model=CharacterRead)
+def get_character(
+    novel_id: int,
+    character_id: int,
+    session: Session = Depends(get_session),
+):
+    return _get_character_or_404(character_id, novel_id, session)
+
+
+@router.patch("/{character_id}", response_model=CharacterRead)
+def update_character(
+    novel_id: int,
+    character_id: int,
+    data: CharacterUpdate,
+    session: Session = Depends(get_session),
+):
+    character = _get_character_or_404(character_id, novel_id, session)
+    update_data = data.model_dump(exclude_unset=True)
+    for key, value in update_data.items():
+        setattr(character, key, value)
+    character.updated_at = datetime.now(timezone.utc)
+    session.add(character)
+    session.commit()
+    session.refresh(character)
+    return character
+
+
+@router.delete("/{character_id}", status_code=204)
+def delete_character(
+    novel_id: int,
+    character_id: int,
+    session: Session = Depends(get_session),
+):
+    character = _get_character_or_404(character_id, novel_id, session)
+    session.delete(character)
+    session.commit()