Render LaTeX formulas with MathJax 3

[hodovani]

This PR integrates MathJax 3 to properly render mathematical expressions in posts, supporting both standard inline/block delimiters ($...$ and $$...$$) and Kramdown compiled math delimiters ((...\) and [...]). MathJax 3 is configured to load asynchronously on all posts automatically.

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PR created automatically by Jules for task 16635535011384213533 started by @hodovani

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