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/adminauth/repository.go

@@ -36,7 +36,7 @@ func NewRepository(db *gorm.DB, redis *redis.Client, jwt *auth.JWTManager) *Repo
 	return &Repository{db: db, redis: redis, jwt: jwt}
 }
 
-func (r *Repository) Captcha() (*CaptchaDTO, error) {
+func (r *Repository) Captcha(ctx context.Context) (*CaptchaDTO, error) {
 	if r.redis == nil {
 		return nil, ErrDependencyUnavailable
 	}
@@ -48,7 +48,6 @@ func (r *Repository) Captcha() (*CaptchaDTO, error) {
 	if err != nil {
 		return nil, err
 	}
-	ctx := context.Background()
 	if err := r.redis.Set(ctx, captchaKey(captchaID), strings.ToUpper(code), captchaTTL).Err(); err != nil {
 		return nil, err
 	}
@@ -59,15 +58,15 @@ func (r *Repository) Captcha() (*CaptchaDTO, error) {
 	}, nil
 }
 
-func (r *Repository) Login(username string, password string, captchaID string, captchaCode string) (LoginResult, error) {
-	if err := r.verifyCaptcha(captchaID, captchaCode); err != nil {
+func (r *Repository) Login(ctx context.Context, username string, password string, captchaID string, captchaCode string) (LoginResult, error) {
+	if err := r.verifyCaptcha(ctx, captchaID, captchaCode); err != nil {
 		return LoginResult{}, err
 	}
-	if err := r.ensureDefaultAdmin(); err != nil {
+	if err := r.ensureDefaultAdmin(ctx); err != nil {
 		return LoginResult{}, err
 	}
 	var admin model.AdminUser
-	if err := r.db.Where("username = ?", username).First(&admin).Error; err != nil {
+	if err := r.db.WithContext(ctx).Where("username = ?", username).First(&admin).Error; err != nil {
 		if errors.Is(err, gorm.ErrRecordNotFound) {
 			return LoginResult{}, ErrInvalidCredential
 		}
@@ -81,7 +80,7 @@ func (r *Repository) Login(username string, password string, captchaID string, c
 	}
 	now := time.Now()
 	admin.LastLoginAt = &now
-	if err := r.db.Save(&admin).Error; err != nil {
+	if err := r.db.WithContext(ctx).Save(&admin).Error; err != nil {
 		return LoginResult{}, err
 	}
 	tokens, err := r.jwt.GenerateSubjectPair(admin.ID, admin.Username, "admin")
@@ -89,15 +88,14 @@ func (r *Repository) Login(username string, password string, captchaID string, c
 		return LoginResult{}, err
 	}
 	dto := toDTO(admin)
-	r.loadRolesAndPerms(&dto)
+	r.loadRolesAndPerms(ctx, &dto)
 	return LoginResult{Admin: dto, Tokens: tokens}, nil
 }
 
-func (r *Repository) verifyCaptcha(captchaID string, captchaCode string) error {
+func (r *Repository) verifyCaptcha(ctx context.Context, captchaID string, captchaCode string) error {
 	if r.redis == nil {
 		return ErrDependencyUnavailable
 	}
-	ctx := context.Background()
 	key := captchaKey(captchaID)
 	stored, err := r.redis.Get(ctx, key).Result()
 	if errors.Is(err, redis.Nil) {
@@ -113,34 +111,34 @@ func (r *Repository) verifyCaptcha(captchaID string, captchaCode string) error {
 	return nil
 }
 
-func (r *Repository) FindByID(id uint64) (*AdminDTO, error) {
+func (r *Repository) FindByID(ctx context.Context, id uint64) (*AdminDTO, error) {
 	var admin model.AdminUser
-	if err := r.db.First(&admin, id).Error; err != nil {
+	if err := r.db.WithContext(ctx).First(&admin, id).Error; err != nil {
 		return nil, err
 	}
 	if admin.Status != "active" {
 		return nil, ErrAdminDisabled
 	}
 	dto := toDTO(admin)
-	r.loadRolesAndPerms(&dto)
+	r.loadRolesAndPerms(ctx, &dto)
 	return &dto, nil
 }
 
-func (r *Repository) UpdateSupportStatus(adminID uint64, status string) error {
+func (r *Repository) UpdateSupportStatus(ctx context.Context, adminID uint64, status string) error {
 	if r.db == nil {
 		return ErrDependencyUnavailable
 	}
 	if status != "online" && status != "offline" && status != "busy" {
 		return errors.New("invalid support status")
 	}
-	return r.db.Model(&model.AdminUser{}).
+	return r.db.WithContext(ctx).Model(&model.AdminUser{}).
 		Where("id = ?", adminID).
 		Update("support_status", status).Error
 }
 
-func (r *Repository) ensureDefaultAdmin() error {
+func (r *Repository) ensureDefaultAdmin(ctx context.Context) error {
 	var count int64
-	if err := r.db.Model(&model.AdminUser{}).Count(&count).Error; err != nil {
+	if err := r.db.WithContext(ctx).Model(&model.AdminUser{}).Count(&count).Error; err != nil {
 		return err
 	}
 	if count > 0 {
@@ -156,14 +154,14 @@ func (r *Repository) ensureDefaultAdmin() error {
 		Nickname:     "超级管理员",
 		Status:       "active",
 	}
-	if err := r.db.Create(&admin).Error; err != nil {
+	if err := r.db.WithContext(ctx).Create(&admin).Error; err != nil {
 		return err
 	}
 
 	// 自动关联 super_admin 角色
 	var superAdminRole model.Role
-	if err := r.db.Where("code = ?", "super_admin").First(&superAdminRole).Error; err == nil {
-		r.db.Create(&model.AdminUserRole{
+	if err := r.db.WithContext(ctx).Where("code = ?", "super_admin").First(&superAdminRole).Error; err == nil {
+		r.db.WithContext(ctx).Create(&model.AdminUserRole{
 			AdminID: admin.ID,
 			RoleID:  superAdminRole.ID,
 		})
@@ -183,13 +181,13 @@ func toDTO(admin model.AdminUser) AdminDTO {
 	}
 }
 
-func (r *Repository) loadRolesAndPerms(dto *AdminDTO) {
+func (r *Repository) loadRolesAndPerms(ctx context.Context, dto *AdminDTO) {
 	if r.db == nil {
 		return
 	}
 	// 加载角色
 	var roles []RoleDTO
-	r.db.Table("roles").
+	r.db.WithContext(ctx).Table("roles").
 		Joins("JOIN admin_user_roles aur ON aur.role_id = roles.id").
 		Where("aur.admin_user_id = ?", dto.ID).
 		Find(&roles)
@@ -205,7 +203,7 @@ func (r *Repository) loadRolesAndPerms(dto *AdminDTO) {
 	}
 
 	var permCodes []string
-	r.db.Table("permissions").
+	r.db.WithContext(ctx).Table("permissions").
 		Select("DISTINCT permissions.code").
 		Joins("JOIN role_permissions rp ON rp.permission_id = permissions.id").
 		Joins("JOIN admin_user_roles aur ON aur.role_id = rp.role_id").