新增文件管理与技能管理功能：

- **文件管理**：
  - 支持文件上传、解析和删除。
  - 限制支持格式（txt, md, docx, pdf），最大 10MB。
  - 提供前端上传区、文件列表及后端解析服务。

- **技能管理**：
  - 新增技能的创建、更新及删除功能。
  - 支持分配自定义提示词和工具权限。
  - 提供技能列表及分组工具选择交互界面。

同时调整相关 API 和前端组件，优化协作体验。

backend/app/routers/skills.py

@@ -0,0 +1,111 @@
+"""Skill 插件管理路由"""
+
+import json
+from datetime import datetime, timezone
+
+from fastapi import APIRouter, HTTPException
+from sqlmodel import Session, select, or_
+
+from ..database import engine
+from ..models import Skill
+from ..schemas import SkillCreate, SkillUpdate, SkillRead, SkillList, ToolInfo
+from ..services.tools import TOOL_DEFINITIONS
+
+router = APIRouter(prefix="/api/skills", tags=["skills"])
+
+
+def _skill_to_read(skill: Skill) -> SkillRead:
+    """将 Skill ORM 对象转为 SkillRead，反序列化 allowed_tools"""
+    try:
+        tools = json.loads(skill.allowed_tools) if skill.allowed_tools else []
+    except (json.JSONDecodeError, TypeError):
+        tools = []
+    return SkillRead(
+        id=skill.id,  # type: ignore
+        name=skill.name,
+        description=skill.description,
+        system_prompt=skill.system_prompt,
+        allowed_tools=tools,
+        is_builtin=skill.is_builtin,
+        novel_id=skill.novel_id,
+        created_at=skill.created_at,
+        updated_at=skill.updated_at,
+    )
+
+
+@router.get("", response_model=SkillList)
+def list_skills(novel_id: int | None = None):
+    """列出 Skill，返回全局 + 指定小说的"""
+    with Session(engine) as session:
+        if novel_id is not None:
+            stmt = (
+                select(Skill)
+                .where(or_(Skill.novel_id.is_(None), Skill.novel_id == novel_id))  # type: ignore
+                .order_by(Skill.is_builtin.desc(), Skill.created_at)  # type: ignore
+            )
+        else:
+            stmt = select(Skill).order_by(Skill.is_builtin.desc(), Skill.created_at)  # type: ignore
+        skills = session.exec(stmt).all()
+        items = [_skill_to_read(s) for s in skills]
+        return SkillList(items=items, total=len(items))
+
+
+@router.post("", response_model=SkillRead, status_code=201)
+def create_skill(data: SkillCreate):
+    """创建 Skill"""
+    with Session(engine) as session:
+        skill = Skill(
+            name=data.name,
+            description=data.description,
+            system_prompt=data.system_prompt,
+            allowed_tools=json.dumps(data.allowed_tools, ensure_ascii=False),
+            is_builtin=False,
+            novel_id=data.novel_id,
+        )
+        session.add(skill)
+        session.commit()
+        session.refresh(skill)
+        return _skill_to_read(skill)
+
+
+@router.get("/tools", response_model=list[ToolInfo])
+def get_available_tools():
+    """返回所有可用工具名和描述（供前端工具 checkbox 使用）"""
+    return [
+        ToolInfo(name=t["name"], description=t["description"])
+        for t in TOOL_DEFINITIONS
+    ]
+
+
+@router.patch("/{skill_id}", response_model=SkillRead)
+def update_skill(skill_id: int, data: SkillUpdate):
+    """更新 Skill"""
+    with Session(engine) as session:
+        skill = session.get(Skill, skill_id)
+        if not skill:
+            raise HTTPException(status_code=404, detail="Skill 不存在")
+
+        if data.name is not None:
+            skill.name = data.name
+        if data.description is not None:
+            skill.description = data.description
+        if data.system_prompt is not None:
+            skill.system_prompt = data.system_prompt
+        if data.allowed_tools is not None:
+            skill.allowed_tools = json.dumps(data.allowed_tools, ensure_ascii=False)
+        skill.updated_at = datetime.now(timezone.utc)
+        session.add(skill)
+        session.commit()
+        session.refresh(skill)
+        return _skill_to_read(skill)
+
+
+@router.delete("/{skill_id}", status_code=204)
+def delete_skill(skill_id: int):
+    """删除 Skill"""
+    with Session(engine) as session:
+        skill = session.get(Skill, skill_id)
+        if not skill:
+            raise HTTPException(status_code=404, detail="Skill 不存在")
+        session.delete(skill)
+        session.commit()