Fix quicksort temporary index buffer leak

[amartinsmg]

Motivation

• Address a memory leak in quicksort where the dynamically allocated rangeIndexes buffer was not freed.

Description

• Add free(rangeIndexes); at the end of quicksort in src/quicksort.hpp to release the temporary index buffer, leaving algorithm behavior unchanged.

Testing

• Built and ran make test and ./debug/test (21 tests) which passed, and ran a randomized fuzz comparison against std::sort for all algorithms which also passed.

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Codex Task