Phase 1: gate the Accounting sidebar item and /dashboard/accounting route
behind isAdmin via a RequireAdmin guard; Financial Reports stay visible.
Phase 2: platform associations now read the Chart of Accounts from
accounting.accounts (single source) instead of public.chart_of_accounts.
Shared fetchChartOfAccounts() normalizes both sources; central COA hooks
and ChartOfAccountsDropdown route through it (reads only, no migration).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
