Phase 3: Bank reconciliation system

Added complete bank statement reconciliation workflow:

Database Schema:
- BankStatement: metadata for uploaded statements
- BankStatementLine: individual transactions from statements
- BankReconciliation: links system transactions to bank lines

Features:
- CSV import with flexible format detection (DD/MM/YYYY, YYYY-MM-DD dates)
- Auto-matching algorithm: exact amount+date = 100% confidence, fuzzy matching up to 7 days
- Manual matching UI for unmatched transactions
- Discrepancy detection (amount mismatches)
- Reconciliation dashboard with summary stats
- Statement history view with status tracking

Pages:
- /admin/accounts/reconciliation: Dashboard and statement list
- /admin/accounts/reconciliation?id=X: Statement detail with matching UI
- /admin/accounts/reconciliation/upload: CSV upload form

Server Actions:
- uploadBankStatement: CSV parsing and auto-matching
- manualMatch: User-initiated transaction linking
- unmatchBankLine: Remove incorrect match
- archiveStatement: Mark statement as complete
- markReconciled: Finalize reconciliation

Utils:
- parseCSV: Flexible bank statement parser
- autoMatchTransactions: Fuzzy matching algorithm
- getReconciliationSummary: Stats calculation

UI Components:
- ReconciliationClient: Interactive matching interface with tabs
- Manual match form: User-friendly transaction linking

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

src/components/AdminMenu.tsx

@@ -7,6 +7,7 @@ import { logoutAdmin } from '@/app/admin/login/actions';
 const ADMIN_LINKS = [
   { href: '/admin/orders', label: 'Orders' },
   { href: '/admin/accounts', label: 'Accounts' },
+  { href: '/admin/accounts/reconciliation', label: 'Bank reconciliation' },
   { href: '/admin/products/new', label: 'Add product' },
   { href: '/admin/products', label: 'All products' },
   { href: '/admin/categories/new', label: 'Add category' },