Add Balance Reconciliation report (detective control)

Phase 1 of the accounting audit remediation. A read-only diagnostic that surfaces
drift in the denormalized balances without changing any posting:

- Per account: stored Account.CurrentBalance vs the balance recomputed from source
  documents (the same LedgerService path RecalculateBalances uses). Drifted rows
  are highlighted; a difference means the cache is stale and a recalc would fix it.
- AR subledger (sum of Customer.CurrentBalance) vs the AR control account, and AP
  subledger (sum of Vendor.CurrentBalance) vs the AP control account.

FinancialReportService now takes ILedgerService to recompute. New
GetBalanceReconciliationAsync + BalanceReconciliationDto, a /Reports/Reconciliation
action, view, and a card on the reports landing. Build clean; 284 unit tests pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/PowderCoating.Infrastructure/Services/FinancialReportService.cs

@@ -19,10 +19,65 @@ namespace PowderCoating.Infrastructure.Services;
 public class FinancialReportService : IFinancialReportService
 {
     private readonly ApplicationDbContext _context;
+    private readonly ILedgerService _ledger;
 
-    public FinancialReportService(ApplicationDbContext context)
+    public FinancialReportService(ApplicationDbContext context, ILedgerService ledger)
     {
         _context = context;
+        _ledger = ledger;
+    }
+
+    /// <inheritdoc/>
+    public async Task<BalanceReconciliationDto> GetBalanceReconciliationAsync(int companyId)
+    {
+        var companyName = await GetCompanyNameAsync(companyId);
+
+        var accounts = await _context.Accounts
+            .Where(a => a.CompanyId == companyId && a.IsActive && !a.IsDeleted)
+            .OrderBy(a => a.AccountNumber)
+            .ToListAsync();
+
+        // Epoch start so LedgerService treats OpeningBalance as prior and all activity falls in-window —
+        // identical to how AccountBalanceService.RecalculateAllAsync derives the authoritative balance.
+        var epoch = new DateTime(2000, 1, 1);
+        var now = DateTime.UtcNow;
+
+        var lines = new List<BalanceReconciliationLine>();
+        decimal arControl = 0m, apControl = 0m;
+        foreach (var a in accounts)
+        {
+            var ledger = await _ledger.GetAccountLedgerAsync(a.Id, epoch, now);
+            var ledgerBalance = ledger?.ClosingBalance ?? 0m;
+            lines.Add(new BalanceReconciliationLine
+            {
+                AccountId = a.Id,
+                AccountNumber = a.AccountNumber,
+                AccountName = a.Name,
+                AccountType = a.AccountType,
+                StoredBalance = a.CurrentBalance,
+                LedgerBalance = ledgerBalance
+            });
+            if (a.AccountSubType == AccountSubType.AccountsReceivable) arControl += ledgerBalance;
+            if (a.AccountSubType == AccountSubType.AccountsPayable) apControl += ledgerBalance;
+        }
+
+        var arSubledger = await _context.Customers
+            .Where(c => c.CompanyId == companyId && !c.IsDeleted)
+            .SumAsync(c => (decimal?)c.CurrentBalance) ?? 0m;
+        var apSubledger = await _context.Vendors
+            .Where(v => v.CompanyId == companyId && !v.IsDeleted)
+            .SumAsync(v => (decimal?)v.CurrentBalance) ?? 0m;
+
+        return new BalanceReconciliationDto
+        {
+            AsOf = now,
+            CompanyName = companyName,
+            AccountLines = lines,
+            ArControlBalance = arControl,
+            ArSubledgerTotal = arSubledger,
+            ApControlBalance = apControl,
+            ApSubledgerTotal = apSubledger
+        };
     }
 
     /// <inheritdoc/>