🔒 Fix potential XSS vulnerability in JSON-LD script tags

[marcin2121]

🎯 What: The vulnerability fixed
In app/layout.tsx, the JSON-LD schema was being injected into a <script> tag using dangerouslySetInnerHTML directly with JSON.stringify(schema).

⚠️ Risk: The potential impact if left unfixed
While the current schema appears to be static or trusted, if any user input were ever to be included in the schema in the future, an attacker could potentially inject a payload like </script><script>alert(1)</script> into a schema field. JSON.stringify does not escape HTML characters, so this payload would break out of the initial <script> tag and execute arbitrary JavaScript, leading to Cross-Site Scripting (XSS).

🛡️ Solution: How the fix addresses the vulnerability
The output of JSON.stringify(schema) is now chained with .replace(/</g, '\\u003c'). This replaces all occurrences of < with its unicode representation \u003c, which is perfectly valid JSON and correctly interpreted by the browser, but prevents the string from being interpreted as an HTML tag like </script>.

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PR created automatically by Jules for task 341306171059743030 started by @marcin2121

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