Enforce quarterly run limit on AI price check

- GET: sets ViewBag.NextRunAvailable if last run was within 90 days;
  view disables the button and shows the next eligible date
- POST: returns early with a warning if called before the 90-day window

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

src/PowderCoating.Web/Controllers/CatalogItemsController.cs

@@ -941,6 +941,13 @@ namespace PowderCoating.Web.Controllers
             var pricedItems = await _unitOfWork.CatalogItems.FindAsync(ci => ci.IsActive && ci.DefaultPrice > 0);
             ViewBag.ActiveItemCount = pricedItems.Count();
 
+            if (report != null)
+            {
+                var nextRun = report.RunAt.AddDays(90);
+                if (nextRun > DateTime.UtcNow)
+                    ViewBag.NextRunAvailable = nextRun.ToLocalTime().ToString("MMMM d, yyyy");
+            }
+
             CatalogPriceCheckReportDto? dto = null;
             if (report != null)
             {
@@ -988,6 +995,20 @@ namespace PowderCoating.Web.Controllers
             var currentUser = await _userManager.GetUserAsync(User);
             if (currentUser == null) return Forbid();
 
+            // Enforce quarterly run limit — check the most recent report for this company.
+            var lastReport = (await _unitOfWork.CatalogPriceCheckReports.FindAsync(
+                r => r.CompanyId == currentUser.CompanyId))
+                .OrderByDescending(r => r.RunAt).FirstOrDefault();
+            if (lastReport != null)
+            {
+                var nextRun = lastReport.RunAt.AddDays(90);
+                if (nextRun > DateTime.UtcNow)
+                {
+                    TempData["Warning"] = $"Price check can only be run once per quarter. Next run available: {nextRun.ToLocalTime():MMMM d, yyyy}.";
+                    return RedirectToAction(nameof(AiPriceCheck));
+                }
+            }
+
             try
             {
                 // Load active catalog items with a real price — skip $0 items (placeholders,