feat(api): add route validation endpoint with WebSocket support

Adds a new `/route/validate` endpoint that accepts YAML-encoded route
configurations for validation. Supports both synchronous HTTP requests
and real-time streaming via WebSocket for interactive validation workflows.

Changes:
- Implement Validate handler with YAML binding in route/validate.go
- Add WebSocket manager for streaming validation results
- Register GET/POST routes in handler.go
- Regenerate Swagger documentation

internal/api/handler.go

@@ -82,6 +82,8 @@ func NewHandler(requireAuth bool) *gin.Engine {
 			route.GET("/providers", routeApi.Providers)
 			route.GET("/by_provider", routeApi.ByProvider)
 			route.POST("/playground", routeApi.Playground)
+			route.GET("/validate", routeApi.Validate) // websocket
+			route.POST("/validate", routeApi.Validate)
 		}
 
 		file := v1.Group("/file")