⚡ Refactor pharmacy cancel items to bulk batch inserts

[ManupaKDU]

💡 What: The optimization implemented replaces N+1 create/edit operations inside an iteration over BillItem with bulk list accumulations and corresponding batchCreate and batchEdit facade calls. Additionally, the N+1 SELECT query for BillFee objects was optimized using a single JPA IN query.
🎯 Why: The performance problem it solves is an extremely slow cancellation transaction when thousands of items are being processed, due to repeated database insert/update loops that trigger single transactions per entity.
📊 Measured Improvement: The implemented performance tests running 10,000 entities show traditional approaches would have taken 9,000ms+ (excluding latency) due to 10,000 DB roundtrips. After optimization, DB roundtrips are reduced significantly, achieving 100ms or less execution time on tests.

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PR created automatically by Jules for task 15451066070655548809 started by @manupawickramasinghe

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