[UI] Update favicon to match documentation site

[idanlodzki]

The favicon on the main website should be identical to the one used on the documentation site:
🔗 https://opsimate.vercel.app/docs/user-management/register-login

Tasks:

Replace the current favicon with the same icon used on the documentation site

Verify it displays correctly on light/dark themes and mobile devices

Confirm proper cache invalidation (use versioned file name if needed)

Ensure favicon appears on browser tabs, bookmarks, and PWA manifest if applicable

Notes:
The goal is to keep a consistent brand identity between the main site and documentation.

[cloudsamrajya]

@idanlodzki /assign