为 9 个模块添加 Context 超时控制

完成模块：
- auth: 3 个 Repository 方法 + Service + Handler + Middleware
- wallet: 已有 context 支持，修复依赖调用
- payment: 已有 context 支持，修复 wallet 调用
- adminaudit: 1 个方法
- notification: 2 个方法
- realname: 2 个方法
- systemconfig: 4 个方法
- adminauth: 7 个方法
- adminuser: 6 个方法

所有数据库调用已改为 r.db.WithContext(ctx)，完整传递 context 链路。

待完成模块: order, listing, chat 等 12 个模块（约 157 个方法）

backend/internal/modules/auth/repository.go

@@ -1,6 +1,7 @@
 package auth
 
 import (
+	"context"
 	"errors"
 	"time"
 
@@ -18,25 +19,25 @@ func NewUserRepository(db *gorm.DB) *UserRepository {
 	return &UserRepository{db: db}
 }
 
-func (r *UserRepository) FindByID(id uint64) (*model.User, error) {
+func (r *UserRepository) FindByID(ctx context.Context, id uint64) (*model.User, error) {
 	var user model.User
-	if err := r.db.First(&user, id).Error; err != nil {
+	if err := r.db.WithContext(ctx).First(&user, id).Error; err != nil {
 		return nil, err
 	}
 	return &user, nil
 }
 
-func (r *UserRepository) UpdateProfile(id uint64, nickname string, avatarURL string) (*model.User, error) {
-	if err := r.db.Model(&model.User{}).Where("id = ?", id).Updates(map[string]any{
+func (r *UserRepository) UpdateProfile(ctx context.Context, id uint64, nickname string, avatarURL string) (*model.User, error) {
+	if err := r.db.WithContext(ctx).Model(&model.User{}).Where("id = ?", id).Updates(map[string]any{
 		"nickname":   nickname,
 		"avatar_url": avatarURL,
 	}).Error; err != nil {
 		return nil, err
 	}
-	return r.FindByID(id)
+	return r.FindByID(ctx, id)
 }
 
-func (r *UserRepository) FindOrCreateByPhone(phone string) (*model.User, error) {
+func (r *UserRepository) FindOrCreateByPhone(ctx context.Context, phone string) (*model.User, error) {
 	now := time.Now()
 	user := model.User{
 		Phone:          phone,
@@ -48,7 +49,7 @@ func (r *UserRepository) FindOrCreateByPhone(phone string) (*model.User, error)
 		LastLoginAt:    &now,
 	}
 
-	err := r.db.Clauses(clause.OnConflict{
+	err := r.db.WithContext(ctx).Clauses(clause.OnConflict{
 		Columns:   []clause.Column{{Name: "phone"}},
 		DoUpdates: clause.AssignmentColumns([]string{"last_login_at", "updated_at"}),
 	}).Create(&user).Error
@@ -57,7 +58,7 @@ func (r *UserRepository) FindOrCreateByPhone(phone string) (*model.User, error)
 	}
 
 	var found model.User
-	if err := r.db.Where("phone = ?", phone).First(&found).Error; err != nil {
+	if err := r.db.WithContext(ctx).Where("phone = ?", phone).First(&found).Error; err != nil {
 		return nil, err
 	}
 	return &found, nil

backend/internal/modules/auth/service.go

@@ -101,7 +101,7 @@ func (s *Service) LoginWithSMS(ctx context.Context, phone string, code string) (
 		return LoginResult{}, err
 	}
 
-	user, err := s.users.FindOrCreateByPhone(phone)
+	user, err := s.users.FindOrCreateByPhone(ctx, phone)
 	if err != nil {
 		return LoginResult{}, err
 	}