Add 4 AI bookkeeping features

Feature 7: Bank Rec Auto-Match — AiSuggestMatches endpoint scores uncleared
transactions vs statement ending balance; AI Auto-Match panel in Reconcile.cshtml
with confidence highlights and Apply All button.

Feature 8: Late Payment Prediction — PredictLatePayments endpoint scores open AR
customers by risk (high/medium/low) using historical avg-days-to-pay + late rate;
rendered as badge table in AR Aging view via ar-aging-ai.js.

Feature 9: Natural Language Financial Queries — FinancialQuery GET page + RunFinancialQuery
POST; 12-month context snapshot pre-loaded; answers grounded in real data with
supporting facts, follow-up suggestions, session history, and example chips.

Feature 10: Recurring Bill Detection — RunRecurringDetection scans 12 months of bills
for vendor payment patterns (monthly/quarterly/annual); card grid view in Bills/RecurringDetection.cshtml
with confidence badges, next-expected-date, and suggested actions.

Supporting: 4 new DTO groups in AccountingAiDtos.cs, 4 method signatures in
IAccountingAiService.cs, 4 implementations in AccountingAiService.cs, 4 new
AiFeatures constants, 2 new Landing page AI report cards.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/PowderCoating.Web/Controllers/BillsController.cs

@@ -1136,6 +1136,68 @@ public class BillsController : Controller
         return Json(result);
     }
 
+    // ── AI: Recurring Bill Detection ──────────────────────────────────────────
+
+    /// <summary>
+    /// GET page — displays the recurring bill detection tool. No data is pre-fetched here;
+    /// the user triggers the scan by clicking a button which calls <see cref="RunRecurringDetection"/>.
+    /// </summary>
+    public IActionResult RecurringDetection() => View();
+
+    /// <summary>
+    /// AJAX POST — loads up to 12 months of bill history for the company and passes it to
+    /// Claude for recurring pattern analysis. Only posted bills (Draft/Open/Partial/Paid) are
+    /// included; Voided bills are excluded so cancelled payments do not distort the pattern.
+    /// Results are returned as JSON for client-side rendering in the view.
+    /// </summary>
+    [HttpPost]
+    [EnableRateLimiting(AppConstants.RateLimitPolicies.Ai)]
+    [ValidateAntiForgeryToken]
+    public async Task<IActionResult> RunRecurringDetection()
+    {
+        try
+        {
+            var companyId = int.TryParse(User.FindFirst("CompanyId")?.Value, out var cid) ? cid : 0;
+            var cutoff = DateTime.Today.AddMonths(-12);
+
+            var bills = (await _unitOfWork.Bills.GetAllAsync(false, b => b.Vendor))
+                .Where(b => b.Status != BillStatus.Voided && b.BillDate >= cutoff)
+                .ToList();
+
+            if (!bills.Any())
+                return Json(new RecurringBillDetectionResult
+                {
+                    Success  = true,
+                    Insights = new List<string> { "No bill history found in the last 12 months." }
+                });
+
+            var companyName = (await _unitOfWork.Companies.GetByIdAsync(companyId))?.CompanyName ?? "Your Company";
+
+            var request = new RecurringBillDetectionRequest
+            {
+                CompanyName = companyName,
+                Bills = bills.Select(b => new RecurringBillHistoryItem
+                {
+                    VendorName  = b.Vendor?.CompanyName ?? $"Vendor #{b.VendorId}",
+                    BillNumber  = b.BillNumber,
+                    Amount      = b.Total,
+                    DateIso     = b.BillDate.ToString("yyyy-MM-dd"),
+                    Memo        = b.Memo
+                }).ToList()
+            };
+
+            var result = await _accountingAi.DetectRecurringBillsAsync(request);
+            var userId = User.FindFirst(System.Security.Claims.ClaimTypes.NameIdentifier)?.Value ?? "";
+            await _usageLogger.LogAsync(companyId, userId, AppConstants.AiFeatures.RecurringBillDetection, result.Success);
+            return Json(result);
+        }
+        catch (Exception ex)
+        {
+            _logger.LogError(ex, "Error running recurring bill detection");
+            return Json(new RecurringBillDetectionResult { Success = false, ErrorMessage = "An error occurred while analyzing bill patterns." });
+        }
+    }
+
     // ── Receipt File Helpers ──────────────────────────────────────────────────
 
     /// <summary>