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/register.go

@@ -63,6 +63,7 @@ func RegisterControllers() *Controllers {
 		Notification: controllers.NewNotificationController(),
 		AppLog:       controllers.NewAppLogController(),
 		SystemWS:     controllers.NewSystemWSController(),
+		WebUI:        controllers.NewWebUIController(services.NewWebUIService(settingsService)),
 	}
 }