init: 毛孩子计划 小程序 + Go 后端 + 内嵌后台

- pets-fe: 微信原生小程序（首页/计划/记录/报告/社区/引导），
  服务端驱动、无假数据；弹层改用 scroll-view，打开时隐藏自定义 tabBar
- pets-be: Gin + GORM(MySQL, sundynix_ 前缀) + MinIO，统一响应/分页，
  微信 code2session 登录，provider-neutral AI(DeepSeek)，go:embed React 后台
- 修复：分段选择类型不匹配（字符串 vs 数字）导致选不中

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

pets-be/internal/service/auth.go

@@ -0,0 +1,122 @@
+package service
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/http"
+	"net/url"
+	"time"
+
+	"gorm.io/gorm"
+
+	"github.com/sundynix/pets-be/internal/model"
+)
+
+// MockLogin 开发态登录：按昵称找回或新建用户
+func (s *Service) MockLogin(nickname string) (*model.User, error) {
+	if nickname == "" {
+		nickname = "毛孩子用户"
+	}
+	var u model.User
+	err := s.db.Where("nickname = ?", nickname).First(&u).Error
+	if errors.Is(err, gorm.ErrRecordNotFound) {
+		u = model.User{Nickname: nickname}
+		if e := s.db.Create(&u).Error; e != nil {
+			return nil, e
+		}
+		return &u, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+	return &u, nil
+}
+
+// code2SessionResp 微信 jscode2session 返回
+type code2SessionResp struct {
+	OpenID     string `json:"openid"`
+	SessionKey string `json:"session_key"`
+	UnionID    string `json:"unionid"`
+	ErrCode    int    `json:"errcode"`
+	ErrMsg     string `json:"errmsg"`
+}
+
+// code2Session 调用微信换取 openid
+func (s *Service) code2Session(code string) (*code2SessionResp, error) {
+	if s.cfg.WeChat.AppID == "" || s.cfg.WeChat.AppSecret == "" {
+		return nil, errors.New("微信登录未配置 app_id / app_secret")
+	}
+	q := url.Values{}
+	q.Set("appid", s.cfg.WeChat.AppID)
+	q.Set("secret", s.cfg.WeChat.AppSecret)
+	q.Set("js_code", code)
+	q.Set("grant_type", "authorization_code")
+	endpoint := "https://api.weixin.qq.com/sns/jscode2session?" + q.Encode()
+
+	ctx, cancel := context.WithTimeout(context.Background(), 8*time.Second)
+	defer cancel()
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
+	if err != nil {
+		return nil, err
+	}
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return nil, err
+	}
+	defer resp.Body.Close()
+
+	var out code2SessionResp
+	if err := json.NewDecoder(resp.Body).Decode(&out); err != nil {
+		return nil, err
+	}
+	if out.ErrCode != 0 {
+		return nil, fmt.Errorf("微信登录失败(%d): %s", out.ErrCode, out.ErrMsg)
+	}
+	if out.OpenID == "" {
+		return nil, errors.New("微信未返回 openid")
+	}
+	return &out, nil
+}
+
+// WechatLogin 微信小程序登录：code → openid → 找回/新建用户
+func (s *Service) WechatLogin(code string) (*model.User, error) {
+	sess, err := s.code2Session(code)
+	if err != nil {
+		return nil, err
+	}
+	var u model.User
+	err = s.db.Where("open_id = ?", sess.OpenID).First(&u).Error
+	if errors.Is(err, gorm.ErrRecordNotFound) {
+		u = model.User{OpenID: sess.OpenID, Nickname: "微信用户"}
+		if e := s.db.Create(&u).Error; e != nil {
+			return nil, e
+		}
+		return &u, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+	return &u, nil
+}
+
+// GetUser 取用户
+func (s *Service) GetUser(userID uint) (*model.User, error) {
+	var u model.User
+	if err := s.db.First(&u, userID).Error; err != nil {
+		if errors.Is(err, gorm.ErrRecordNotFound) {
+			return nil, ErrNotFound
+		}
+		return nil, err
+	}
+	return &u, nil
+}
+
+// UpdateUser 更新用户资料（昵称/头像/手机号）
+func (s *Service) UpdateUser(userID uint, fields map[string]any) (*model.User, error) {
+	if err := s.db.Model(&model.User{}).Where("id = ?", userID).Updates(fields).Error; err != nil {
+		return nil, err
+	}
+	return s.GetUser(userID)
+}