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.Infrastructure/Services/SubscriptionService.cs

@@ -323,6 +323,19 @@ public class SubscriptionService : ISubscriptionService
     /// (3) monthly usage quota from <see cref="GetAiPhotoQuoteUsageAsync"/>.
     /// Comped companies bypass all three gates.
     /// </summary>
+    public async Task<bool> CanUseAiCatalogPriceCheckAsync(int companyId)
+    {
+        var (company, config) = await GetCompanyAndConfigAsync(companyId);
+        if (company == null) return false;
+        if (company.IsComped) return true;
+
+        // Plan-level gate: Enterprise plan must have this feature enabled
+        if (config != null && !config.AllowAiCatalogPriceCheck) return false;
+
+        // Company-level toggle: SuperAdmin can disable per company
+        return company.AiCatalogPriceCheckEnabled;
+    }
+
     public async Task<bool> CanUseAiPhotoQuoteAsync(int companyId)
     {
         var (company, config) = await GetCompanyAndConfigAsync(companyId);