Expense Repository

Repository layer responsible for all CRUD operations on the `travel_expense_reports` and `expense_items` Supabase tables with RLS policies scoped to the submitting user. Handles creating new expense reports, appending expense items, fetching report history, and updating approval status.

Feature: Travel Reimbursement Registration

expense-repository

• Create new travel expense reports in Supabase with correct user scoping via RLS
• Insert individual expense items linked to a parent expense report
• Fetch expense report history for the authenticated user
• Handle optimistic updates and error rollback for offline-tolerant UX