Fix: Disable horizontal scroll in large boards (Fixes #1786)

[Thermo041]

Fix:
Disable horizontal scroll in large boards (Fixes #1786)

Summary:
Fixes #1786 by applying CSS rules to prevent horizontal scrolling in large boards.

Changes Made:

• Updated Board.css and index.css to use:
  • overflow-x: hidden;
  • max-width: 100vw;
• Verified using DevTools that no elements overflow the viewport.

Tested On:

• ✅ Chrome
• ✅ Firefox

Horizontal scrollbar is now removed, resolving the issue.

Fixes #1786

[Thermo041]

Hi! Apologies for not commenting earlier — I noticed this issue and already created a fix. I’m new to open-source and still learning the process.
Please review my PR (#1971) when you get time. I'd love to improve it if needed. Thanks!