[ZLlele]

Fixes #1930

Summary

Use document.body.classList.add('dark') when restoring dark mode from localStorage.

The previous implementation assigned document.body.className = 'dark', which removed any existing classes on the <body> element, such as layout or accessibility classes.

Changes

• Preserve existing <body> classes when dark mode is initialized.
• Keep the existing dark mode toggle behavior unchanged.

Validation

• Verified that existing body classes are preserved when dark mode is restored.
• Verified that the dark class is added correctly.
• Verified that disabling dark mode removes only the dark class.
• Ran git diff --check.

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