[BUG] No state persistence - flowcharts lost on page refresh

[rohitkumarnaidu]

Bug Description

The entire flowchart state (blocks array) is stored only in React useState. Page refresh or accidental tab close permanently loses all work.

Steps to Reproduce

1. Create a complex flowchart with 10+ blocks
2. Press F5 or refresh the browser
3. All blocks are gone - demo flowchart is shown instead

Expected Behavior

• Auto-save blocks to localStorage on every change
• Restore saved flowchart on page load
• Show a New Flowchart button to explicitly start fresh

Suggested Fix

Add useEffect to save blocks to localStorage on change, and initialize state from localStorage.

[rohitkumarnaidu]

Hey maintainer, I'd love to work on this issue and submit a PR. Could you please assign it to me?