Add three-layer feature gating for AI Catalog Price Check

Adds platform-level, plan-level (Enterprise only), and per-company
toggles for the AI Catalog Price Check feature. Includes:
- Company.AiCatalogPriceCheckEnabled per-company flag
- SubscriptionPlanConfig.AllowAiCatalogPriceCheck plan-level flag
- PlatformSetting 'AiCatalogPriceCheckEnabled' global kill switch
- IPlatformSettingsService.GetBoolAsync helper
- ISubscriptionService.CanUseAiCatalogPriceCheckAsync
- UI controls in Companies/Edit, PlatformSubscription/Edit+Index,
  and SubscriptionManagement/Manage
- Migration AddAiCatalogPriceCheckGating applied

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

src/PowderCoating.Web/Controllers/CatalogItemsController.cs

@@ -39,6 +39,7 @@ namespace PowderCoating.Web.Controllers
         private readonly ISubscriptionService _subscriptionService;
         private readonly ICatalogImageService _catalogImageService;
         private readonly IAiCatalogPriceCheckService _priceCheckService;
+        private readonly IPlatformSettingsService _platformSettings;
 
         public CatalogItemsController(
             IUnitOfWork unitOfWork,
@@ -50,7 +51,8 @@ namespace PowderCoating.Web.Controllers
             IMeasurementConversionService measurementService,
             ISubscriptionService subscriptionService,
             ICatalogImageService catalogImageService,
-            IAiCatalogPriceCheckService priceCheckService)
+            IAiCatalogPriceCheckService priceCheckService,
+            IPlatformSettingsService platformSettings)
         {
             _unitOfWork = unitOfWork;
             _mapper = mapper;
@@ -62,6 +64,7 @@ namespace PowderCoating.Web.Controllers
             _subscriptionService = subscriptionService;
             _catalogImageService = catalogImageService;
             _priceCheckService = priceCheckService;
+            _platformSettings = platformSettings;
         }
 
         /// <summary>
@@ -934,6 +937,11 @@ namespace PowderCoating.Web.Controllers
             var currentUser = await _userManager.GetUserAsync(User);
             if (currentUser == null) return Forbid();
 
+            // Three-layer gate: platform setting → plan (Enterprise) → per-company toggle
+            var platformEnabled = await _platformSettings.GetBoolAsync(PlatformSettingKeys.AiCatalogPriceCheckEnabled, true);
+            var companyEnabled = platformEnabled && await _subscriptionService.CanUseAiCatalogPriceCheckAsync(currentUser.CompanyId);
+            ViewBag.AiPriceCheckEnabled = companyEnabled;
+
             var existing = await _unitOfWork.CatalogPriceCheckReports.FindAsync(
                 r => r.CompanyId == currentUser.CompanyId);
             var report = existing.OrderByDescending(r => r.RunAt).FirstOrDefault();
@@ -995,6 +1003,14 @@ namespace PowderCoating.Web.Controllers
             var currentUser = await _userManager.GetUserAsync(User);
             if (currentUser == null) return Forbid();
 
+            // Three-layer gate: platform setting → plan → per-company toggle
+            var platformEnabled = await _platformSettings.GetBoolAsync(PlatformSettingKeys.AiCatalogPriceCheckEnabled, true);
+            if (!platformEnabled || !await _subscriptionService.CanUseAiCatalogPriceCheckAsync(currentUser.CompanyId))
+            {
+                TempData["Error"] = "AI Catalog Price Check is not available on your current plan.";
+                return RedirectToAction(nameof(AiPriceCheck));
+            }
+
             // Enforce quarterly run limit — check the most recent report for this company.
             var lastReport = (await _unitOfWork.CatalogPriceCheckReports.FindAsync(
                 r => r.CompanyId == currentUser.CompanyId))