Group multiple existing transactions together for better organization - pure UI feature that doesn’t affect balances.
Use case: Bank imports often split transactions (e.g., $1000 withdrawal → 10x $100 P2P transfers). Group them to view as a single logical transaction.
Features:
• Create/delete groups from selected transactions
• Collapsed/expanded group display in transaction list
• Group metadata: name, note, totals, transaction count
• Frontend deduplication with auto-loading
• Ungroup preserves all transactions
API endpoints: POST/GET/DELETE /transaction-groups
Key principle: Groups are organizational metadata only - don’t create new transactions or modify balances.
