Render Codeforces statement math markup

[enlorik]

Motivation

• Problem statements from Codeforces often include pre-rendered math markup that was lost when parsing to plain text, making equations and symbols unreadable in the app.
• Preserve safe, minimal HTML fragments so math-related markup like tex-span, sup, and sub can be rendered in the workspace while still stripping unsafe elements.

Description

• Added a conservative HTML sanitizer safeHtml with ALLOWED_TAGS and ALLOWED_CLASS_PREFIXES to preserve Codeforces' math-related elements while removing scripts, styles, links and other unsafe attributes in cfStatementParser.js.
• Returned new fields statementHtml, inputSpecificationHtml, and outputSpecificationHtml from parseCFProblemStatement alongside the existing plain-text fields to remain backward-compatible.
• Updated the problem workspace to render sanitized HTML via a new StatementHtml component that uses dangerouslySetInnerHTML and falls back to plain text when HTML is not available in src/components/ProblemWorkspace.jsx.
• Added CSS adjustments in src/components/ProblemWorkspace.css to improve spacing and prevent inline math fragments from wrapping awkwardly.
• Extended tests in cfStatementParser.test.js to assert the presence and sanitization of preserved math markup.

Testing

• Ran npm test -- cfStatementParser.test.js and the parser test file passed (all tests succeeded).
• Ran npm run lint and the linter completed without errors.
• Ran npm run build and the production build completed successfully.

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Codex Task