Optimize duplicate detection to only query existing transactions within the date range of the uploaded CSV file (plus 1-day buffer). This prevents loading the entire transaction history into memory when checking duplicates. For example, uploading 2800 transactions from Jan-Mar 2024 will now only load existing transactions from that period rather than all historical transactions. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>