Xero connector — add support for P&L (Income Statement) and financial report endpoints Summary:#1812

Access to Xero’s financial report API endpoints, specifically:

GET /Reports/ProfitAndLoss — to pull the Income Statement with YTD totals
Optionally GET /Reports/BalanceSheet — for balance sheet data

Both endpoints exist in the Xero API and return pre-aggregated, deduplicated financial report data exactly as shown in Xero’s interface — which would eliminate the double-counting issue entirely.