Read Costpoint Chart of Accounts

Fetch chart of accounts from Costpoint API for mapping target selection.

Note: - Use Costpoint API to fetch account list - Store accounts with: account code (hierarchical format like 100-001), account name, account type - Support Costpoint's hierarchical account structure (e.g., 100-001, 600-001) - Load accounts when configuration UI session starts - Provide "Refresh Accounts" action to reload from Costpoint on demand - Cache accounts in session/memory for performance - Account types should distinguish balance sheet vs P&L accounts (for project code rules) - Handle Costpoint authentication (existing connector)

Open questions: - What Costpoint API endpoint provides chart of accounts? - What's the authentication method for Costpoint API? - Should accounts be persisted to database or only cached in session?