feat(settings): add default subscriptions for new users

- add default subscriptions to admin settings

- auto-assign subscriptions on register and admin user creation

- add validation/tests and align settings UI with subscription selector patterns

backend/internal/handler/admin/setting_handler.go

@@ -51,6 +51,13 @@ func (h *SettingHandler) GetSettings(c *gin.Context) {
 
 	// Check if ops monitoring is enabled (respects config.ops.enabled)
 	opsEnabled := h.opsService != nil && h.opsService.IsMonitoringEnabled(c.Request.Context())
+	defaultSubscriptions := make([]dto.DefaultSubscriptionSetting, 0, len(settings.DefaultSubscriptions))
+	for _, sub := range settings.DefaultSubscriptions {
+		defaultSubscriptions = append(defaultSubscriptions, dto.DefaultSubscriptionSetting{
+			GroupID:      sub.GroupID,
+			ValidityDays: sub.ValidityDays,
+		})
+	}
 
 	response.Success(c, dto.SystemSettings{
 		RegistrationEnabled:                  settings.RegistrationEnabled,
@@ -87,6 +94,7 @@ func (h *SettingHandler) GetSettings(c *gin.Context) {
 		SoraClientEnabled:                    settings.SoraClientEnabled,
 		DefaultConcurrency:                   settings.DefaultConcurrency,
 		DefaultBalance:                       settings.DefaultBalance,
+		DefaultSubscriptions:                 defaultSubscriptions,
 		EnableModelFallback:                  settings.EnableModelFallback,
 		FallbackModelAnthropic:               settings.FallbackModelAnthropic,
 		FallbackModelOpenAI:                  settings.FallbackModelOpenAI,
@@ -146,8 +154,9 @@ type UpdateSettingsRequest struct {
 	SoraClientEnabled           bool    `json:"sora_client_enabled"`
 
 	// 默认配置
-	DefaultConcurrency int     `json:"default_concurrency"`
-	DefaultBalance     float64 `json:"default_balance"`
+	DefaultConcurrency   int     `json:"default_concurrency"`
+	DefaultBalance       float64 `json:"default_balance"`
+	DefaultSubscriptions []dto.DefaultSubscriptionSetting `json:"default_subscriptions"`
 
 	// Model fallback configuration
 	EnableModelFallback      bool   `json:"enable_model_fallback"`
@@ -194,6 +203,7 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 	if req.SMTPPort <= 0 {
 		req.SMTPPort = 587
 	}
+	req.DefaultSubscriptions = normalizeDefaultSubscriptions(req.DefaultSubscriptions)
 
 	// Turnstile 参数验证
 	if req.TurnstileEnabled {
@@ -300,6 +310,13 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 		}
 		req.OpsMetricsIntervalSeconds = &v
 	}
+	defaultSubscriptions := make([]service.DefaultSubscriptionSetting, 0, len(req.DefaultSubscriptions))
+	for _, sub := range req.DefaultSubscriptions {
+		defaultSubscriptions = append(defaultSubscriptions, service.DefaultSubscriptionSetting{
+			GroupID:      sub.GroupID,
+			ValidityDays: sub.ValidityDays,
+		})
+	}
 
 	// 验证最低版本号格式（空字符串=禁用，或合法 semver）
 	if req.MinClaudeCodeVersion != "" {
@@ -343,6 +360,7 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 		SoraClientEnabled:           req.SoraClientEnabled,
 		DefaultConcurrency:          req.DefaultConcurrency,
 		DefaultBalance:              req.DefaultBalance,
+		DefaultSubscriptions:        defaultSubscriptions,
 		EnableModelFallback:         req.EnableModelFallback,
 		FallbackModelAnthropic:      req.FallbackModelAnthropic,
 		FallbackModelOpenAI:         req.FallbackModelOpenAI,
@@ -390,6 +408,13 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 		response.ErrorFrom(c, err)
 		return
 	}
+	updatedDefaultSubscriptions := make([]dto.DefaultSubscriptionSetting, 0, len(updatedSettings.DefaultSubscriptions))
+	for _, sub := range updatedSettings.DefaultSubscriptions {
+		updatedDefaultSubscriptions = append(updatedDefaultSubscriptions, dto.DefaultSubscriptionSetting{
+			GroupID:      sub.GroupID,
+			ValidityDays: sub.ValidityDays,
+		})
+	}
 
 	response.Success(c, dto.SystemSettings{
 		RegistrationEnabled:                  updatedSettings.RegistrationEnabled,
@@ -426,6 +451,7 @@ func (h *SettingHandler) UpdateSettings(c *gin.Context) {
 		SoraClientEnabled:                    updatedSettings.SoraClientEnabled,
 		DefaultConcurrency:                   updatedSettings.DefaultConcurrency,
 		DefaultBalance:                       updatedSettings.DefaultBalance,
+		DefaultSubscriptions:                 updatedDefaultSubscriptions,
 		EnableModelFallback:                  updatedSettings.EnableModelFallback,
 		FallbackModelAnthropic:               updatedSettings.FallbackModelAnthropic,
 		FallbackModelOpenAI:                  updatedSettings.FallbackModelOpenAI,
@@ -547,6 +573,9 @@ func diffSettings(before *service.SystemSettings, after *service.SystemSettings,
 	if before.DefaultBalance != after.DefaultBalance {
 		changed = append(changed, "default_balance")
 	}
+	if !equalDefaultSubscriptions(before.DefaultSubscriptions, after.DefaultSubscriptions) {
+		changed = append(changed, "default_subscriptions")
+	}
 	if before.EnableModelFallback != after.EnableModelFallback {
 		changed = append(changed, "enable_model_fallback")
 	}
@@ -586,6 +615,35 @@ func diffSettings(before *service.SystemSettings, after *service.SystemSettings,
 	return changed
 }
 
+func normalizeDefaultSubscriptions(input []dto.DefaultSubscriptionSetting) []dto.DefaultSubscriptionSetting {
+	if len(input) == 0 {
+		return nil
+	}
+	normalized := make([]dto.DefaultSubscriptionSetting, 0, len(input))
+	for _, item := range input {
+		if item.GroupID <= 0 || item.ValidityDays <= 0 {
+			continue
+		}
+		if item.ValidityDays > service.MaxValidityDays {
+			item.ValidityDays = service.MaxValidityDays
+		}
+		normalized = append(normalized, item)
+	}
+	return normalized
+}
+
+func equalDefaultSubscriptions(a, b []service.DefaultSubscriptionSetting) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for i := range a {
+		if a[i].GroupID != b[i].GroupID || a[i].ValidityDays != b[i].ValidityDays {
+			return false
+		}
+	}
+	return true
+}
+
 // TestSMTPRequest 测试SMTP连接请求
 type TestSMTPRequest struct {
 	SMTPHost     string `json:"smtp_host" binding:"required"`