feat(api): add log webhook notification service

Implement webhook notifications for log error threshold alerts with
configurable thresholds, time windows, and cooldown periods.

- Add LogWebhookService with Redis-backed configuration storage
- Add admin endpoints for webhook config management (GET/PUT)
- Trigger webhook notifications when error count exceeds threshold
- Support status code threshold and error message detection
- Include sample log record data in webhook payload

cmd/server/main.go

@@ -218,6 +218,8 @@ func main() {
 		adminGroup.GET("/logs", handler.ListLogs)
 		adminGroup.DELETE("/logs", handler.DeleteLogs)
 		adminGroup.GET("/logs/stats", handler.LogStats)
+		adminGroup.GET("/logs/webhook", handler.GetLogWebhookConfig)
+		adminGroup.PUT("/logs/webhook", handler.UpdateLogWebhookConfig)
 		adminGroup.GET("/stats", adminHandler.GetAdminStats)
 		adminGroup.POST("/bindings", handler.CreateBinding)
 		adminGroup.GET("/bindings", handler.ListBindings)