Render Codeforces math in Problem Workspace

[enlorik]

@copilot please create a PR for this issue.

Bug:
In the HDD Codeforces Problem Workspace, problem statements show raw TeX markers like $$$n$$$ instead of rendered math. Codeforces normally renders those markers as math, but HDD currently displays the delimiters as text.

Goal:
Render math inside the Problem Workspace statement panel.

Requirements:

• Support Codeforces-style $$$...$$$ math markers.
• Also support common TeX markers like $...$, \(...\), and \[...\] if easy.
• Render math only in statement text, input specification, and output specification.
• Do not render math inside sample input/output blocks or the Kotlin editor.
• Keep the server returning structured statement data; do not switch the frontend to raw Codeforces HTML.
• Keep the PR focused. Do not add code execution, submission, login, or unrelated refactors.
• If adding a dependency such as KaTeX or MathJax, update package.json and package-lock.json correctly.
• Add helper tests if a math parsing/render helper is introduced.

Validation:

• npm test
• npm run lint
• npm run build

Purpose:
The Problem Workspace should hide Codeforces formatting internals and show readable math inside HDD.