docs(readme): 编写项目README文档，描述功能与架构

- 完整撰写玉宗珠宝设计大师项目README，介绍项目概况及核心功能
- 说明用户认证系统实现及优势，包含JWT鉴权和密码加密细节
- 详细描述品类管理系统，支持多流程类型和多种玉石品类
- 说明设计图生成方案及技术，包含Pillow生成示例及字体支持
- 介绍设计管理功能，支持分页浏览、预览、下载和删除设计
- 个人信息管理模块说明，涵盖昵称、手机号、密码的安全修改
- 绘制业务流程图和关键数据流图，清晰展现系统架构与数据流
- 提供详细API调用链路及参数说明，涵盖用户、品类、设计接口
- 列明技术栈及版本，包含前后端框架、ORM、认证、加密等工具
- 展示目录结构，标明后端与前端项目布局
- 规划本地开发环境与启动步骤，包括数据库初始化及运行命令
- 说明服务器部署流程和Nginx配置方案
- 详细数据库表结构说明及环境变量配置指导
- 汇总常用开发及测试命令，方便开发调试与部署管理

backend/app/routers/designs.py

@@ -0,0 +1,201 @@
+"""
+设计相关路由
+提供设计生成、查询、删除、下载接口
+"""
+import os
+from fastapi import APIRouter, Depends, HTTPException, status, Query
+from fastapi.responses import FileResponse
+from sqlalchemy.orm import Session
+
+from ..database import get_db
+from ..models import User, Design
+from ..schemas import DesignCreate, DesignResponse, DesignListResponse
+from ..utils.deps import get_current_user
+from ..services import design_service
+
+router = APIRouter(prefix="/api/designs", tags=["设计"])
+
+
+def design_to_response(design: Design) -> DesignResponse:
+    """将 Design 模型转换为响应格式"""
+    return DesignResponse(
+        id=design.id,
+        user_id=design.user_id,
+        category={
+            "id": design.category.id,
+            "name": design.category.name,
+            "icon": design.category.icon,
+            "sort_order": design.category.sort_order,
+            "flow_type": design.category.flow_type
+        },
+        sub_type={
+            "id": design.sub_type.id,
+            "category_id": design.sub_type.category_id,
+            "name": design.sub_type.name,
+            "description": design.sub_type.description,
+            "preview_image": design.sub_type.preview_image,
+            "sort_order": design.sub_type.sort_order
+        } if design.sub_type else None,
+        color={
+            "id": design.color.id,
+            "category_id": design.color.category_id,
+            "name": design.color.name,
+            "hex_code": design.color.hex_code,
+            "sort_order": design.color.sort_order
+        } if design.color else None,
+        prompt=design.prompt,
+        carving_technique=design.carving_technique,
+        design_style=design.design_style,
+        motif=design.motif,
+        size_spec=design.size_spec,
+        surface_finish=design.surface_finish,
+        usage_scene=design.usage_scene,
+        image_url=design.image_url,
+        status=design.status,
+        created_at=design.created_at,
+        updated_at=design.updated_at
+    )
+
+
+@router.post("/generate", response_model=DesignResponse)
+def generate_design(
+    design_data: DesignCreate,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user)
+):
+    """
+    提交设计生成请求
+    需要认证
+    """
+    try:
+        design = design_service.create_design(
+            db=db,
+            user_id=current_user.id,
+            design_data=design_data
+        )
+        return design_to_response(design)
+    except ValueError as e:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=str(e)
+        )
+
+
+@router.get("", response_model=DesignListResponse)
+def get_designs(
+    page: int = Query(1, ge=1, description="页码"),
+    page_size: int = Query(20, ge=1, le=100, description="每页数量"),
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user)
+):
+    """
+    获取当前用户的设计历史列表（分页）
+    需要认证
+    """
+    designs, total = design_service.get_user_designs(
+        db=db,
+        user_id=current_user.id,
+        page=page,
+        page_size=page_size
+    )
+    
+    return DesignListResponse(
+        items=[design_to_response(d) for d in designs],
+        total=total,
+        page=page,
+        page_size=page_size
+    )
+
+
+@router.get("/{design_id}", response_model=DesignResponse)
+def get_design(
+    design_id: int,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user)
+):
+    """
+    获取设计详情
+    只能查看自己的设计，非本人设计返回 404
+    """
+    design = design_service.get_design_by_id(
+        db=db,
+        design_id=design_id,
+        user_id=current_user.id
+    )
+    
+    if not design:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="设计不存在"
+        )
+    
+    return design_to_response(design)
+
+
+@router.delete("/{design_id}")
+def delete_design(
+    design_id: int,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user)
+):
+    """
+    删除设计
+    只能删除自己的设计，非本人设计返回 404
+    """
+    success = design_service.delete_design(
+        db=db,
+        design_id=design_id,
+        user_id=current_user.id
+    )
+    
+    if not success:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="设计不存在"
+        )
+    
+    return {"message": "删除成功"}
+
+
+@router.get("/{design_id}/download")
+def download_design(
+    design_id: int,
+    db: Session = Depends(get_db),
+    current_user: User = Depends(get_current_user)
+):
+    """
+    下载设计图
+    只能下载自己的设计，非本人设计返回 404
+    """
+    design = design_service.get_design_by_id(
+        db=db,
+        design_id=design_id,
+        user_id=current_user.id
+    )
+    
+    if not design:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="设计不存在"
+        )
+    
+    if not design.image_url:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="设计图片不存在"
+        )
+    
+    # 转换 URL 为文件路径
+    file_path = design.image_url.lstrip("/")
+    
+    if not os.path.exists(file_path):
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="设计图片文件不存在"
+        )
+    
+    return FileResponse(
+        path=file_path,
+        filename=f"design_{design_id}.png",
+        media_type="image/png"
+    )