feat: support for dark mode

[khareyash05]

What does this PR do?

Fixes #941

Type of change

• Bug fix (non-breaking change which fixes an issue)
• Chore (refactoring code, technical debt, workflow improvements)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (does not change functionality, e.g. code style improvements, linting)
• This change requires a documentation update

Mandatory Tasks

• Make sure you have self-reviewed the code. A decent size PR without self-review might be rejected.

Checklist

[vercel]

@khareyash05 is attempting to deploy a commit to the langfuse Team on Vercel.

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