Transactions groups

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.