feat: implement custom WebUI support with dynamic frontend replacement

- Add WebUI service and controller for managing custom frontend packages

- Allow overriding default static assets when custom WebUI is activated

- Add Make commands for packing custom WebUI distributions

- Update UI settings to support uploading, activating and deleting WebUIs

- Document WebUI feature in README and changelog

internal/router/router.go

@@ -30,6 +30,7 @@ type Controllers struct {
 	Notification *controllers.NotificationController
 	AppLog       *controllers.AppLogController
 	SystemWS     *controllers.SystemWSController
+	WebUI        *controllers.WebUIController
 }
 
 func Setup(c *Controllers) *gin.Engine {