Feature: Implement Undo/Redo history support in VisualCircuit editor

## Description

While experimenting with VisualCircuit locally, I noticed that the editor
does not provide undo or redo functionality when modifying circuits.

Currently actions such as:

- adding blocks
- deleting blocks
- moving blocks
- creating connections
- deleting connections

cannot be reverted easily.

For a visual programming environment this can lead to accidental loss of
work and makes experimentation harder.

## Proposed Improvement

Introduce an undo/redo system for the VisualCircuit editor.

Suggested behavior:

- `Ctrl + Z` → Undo last action
- `Ctrl + Shift + Z` → Redo action
- maintain a history stack of editor state changes
- support undo/redo for block creation, deletion, movement and connections

## Benefits

- safer editing experience
- improved productivity when building circuits
- aligns VisualCircuit with modern node-based editors such as Node-RED
and other visual programming environments

## Screenshot