⚡ Bolt: Replace O(N²) list inclusion checks with O(N) set lookups

[mapleleaflatte03]

💡 What: Replaced seen = [] with seen = set() for deduplication in blocking_commitment_ids and blocked_peer_host_ids.
🎯 Why: Checking inclusion against a list (if item not in seen:) inside a loop causes O(N²) time complexity. Using a set provides O(1) lookups, bringing the overall complexity down to O(N).
📊 Impact: Measurably faster execution for accounts with many cases/commitments. Reduces CPU overhead.
🔬 Measurement: Run the test suite for kernel and meridian_platform to ensure correctness, and benchmark execution time for accounts with thousands of commitments.

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PR created automatically by Jules for task 711452392405525343 started by @mapleleaflatte03

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