⚡ Optimize DOM traversal in i18n replacement

[cmuench]

💡 What:

• Replaced document.querySelectorAll('*') with document.createTreeWalker(document.documentElement, NodeFilter.SHOW_ELEMENT) in replaceI18nPlaceholders.
• Optimized attribute iteration by using a standard for loop over el.attributes instead of Array.from(el.attributes).forEach.
• Updated tests/utils.test.js to expose NodeFilter in the test environment.

🎯 Why:

• document.querySelectorAll('*') forces the browser to visit every node and create a static NodeList, which is O(N) memory and time.
• TreeWalker allows traversing the DOM without allocating a large list of nodes.
• Avoiding Array.from for attributes reduces temporary object allocation during traversal.

📊 Measured Improvement:

• Baseline: ~101ms (average over 5 runs with 5000 elements in JSDOM)
• Optimized: ~68ms (average over 5 runs with 5000 elements in JSDOM)
• Improvement: ~33% reduction in execution time.

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PR created automatically by Jules for task 507795617736555274 started by @cmuench

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