This commit introduces the necessary logic and UI controls to allow users to switch the Flow component layout between vertical and horizontal orientations.
* **`Flow.svelte` Refactoring:**
* Updates logic for calculating level offsets and node positions to consistently respect the current flow orientation.
* Adds a control panel using `<Controls>` and `<SwitchButton>` components.
* Provides user interface elements to easily switch the flow layout between horizontal and vertical orientations.