⚡ Bolt: O(N) single-pass answer fragment reassembly

[vamzi]

💡 What:
Refactored the fragmented answer packet reassembly in decode_answer_fragments_from_packet to use an O(N) single-pass bucket-sort algorithm over packet.all_resource_records(). It allocates a fixed-size [Option<DecodedFragment>; 256] array on the stack using a const initializer to completely avoid heap-allocation or Copy/Clone bounds.

🎯 Why:
The original implementation reassembled fragmented DNS answer packets by iteratively calling collect_single_txt in a loop, walking the packet's resource record list up to chunk_total times. In pathological cases with up to 255 fragments, this led to an O(N²) quadratic time complexity.

📊 Impact:
Transforms reassembly performance from O(N²) to O(N) time complexity with zero heap allocations, yielding massive performance gains as the number of fragments increases, while maintaining 100% backward compatibility and exact error propagation.

🔬 Measurement:
Run cargo test -p openhost-pkarr to execute the comprehensive test suite verifying the optimization's correctness under nominal, malformed, and duplicate fragment scenarios.

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PR created automatically by Jules for task 12193032883361170609 started by @vamzi

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