⚡ Performance Optimization: Eliminate Repeated Regex Compilation in TextUtils

[Aatricks]

💡 What:
Moved all inline Regex instantiations in TextUtils.kt (including extractChapterLabel, removeCommonJunk, removeChapterMarkers, cleanSeparators, extractChapterLabelFromUrl, and cleanChapterTitle) to static private val constants. Also added a localized benchmark test TextUtilsBenchmarkTest to measure the overhead and verify the gains.

🎯 Why:
The previous implementation repeatedly compiled regular expressions during heavy loops and common formatting tasks, causing unnecessary overhead and memory allocations.

📊 Measured Improvement:
Baseline extractChapterLabel (for 700,000 invocations): ~1532ms
Optimized extractChapterLabel (for 700,000 invocations): ~752ms
Net Performance Improvement: ~50% faster string processing time in this specific codepath. All tests pass successfully and no regressions were introduced.

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PR created automatically by Jules for task 4321083949119375042 started by @Aatricks

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