fix: merge 5 PR-related improvements

- gateway_handler: pass ParsedRequest to RecordUsage + set in gin.Context
- channel_handler: add FeaturesConfig to CRUD (WebSearch channel toggle)
- channel_repo: features_config JSONB persistence (Create/Get/Update/List)
- security_headers: add Stripe CSP domains (script-src + frame-src)

backend/internal/handler/gateway_handler.go

@@ -473,6 +473,7 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 			h.submitUsageRecordTask(func(ctx context.Context) {
 				if err := h.gatewayService.RecordUsage(ctx, &service.RecordUsageInput{
 					Result:             result,
+					ParsedRequest:      parsedReq,
 					APIKey:             apiKey,
 					User:               apiKey.User,
 					Account:            account,
@@ -675,6 +676,7 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 			}
 
 			// 转发请求 - 根据账号平台分流
+			c.Set("parsed_request", parsedReq)
 			var result *service.ForwardResult
 			requestCtx := c.Request.Context()
 			if fs.SwitchCount > 0 {
@@ -813,6 +815,7 @@ func (h *GatewayHandler) Messages(c *gin.Context) {
 			h.submitUsageRecordTask(func(ctx context.Context) {
 				if err := h.gatewayService.RecordUsage(ctx, &service.RecordUsageInput{
 					Result:             result,
+					ParsedRequest:      parsedReq,
 					APIKey:             currentAPIKey,
 					User:               currentAPIKey.User,
 					Account:            account,