Commit remaining unstaged changes from this session

- Platform settings service: IPlatformSettingsService, PlatformSettingKeys,
  PlatformSettingsService, SubscriptionService, AppConstants,
  SubscriptionExpiryBackgroundService, SubscriptionMiddleware
- JobTimeEntry entity, DTOs, AutoMapper profile (ShopWorker → UserId migration)
- InventoryDtos: SourceTransactionId on PowderUsageLogDto
- InventoryTransactionRepository: include Job.Customer in ledger query
- InventoryAiLookupService: @graph unwrap + HTML price fallback
- ApplicationDbContextModelSnapshot: reflect migration changes
- launchSettings.json, publish profile

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

src/PowderCoating.Core/Entities/JobTimeEntry.cs

@@ -3,7 +3,9 @@ namespace PowderCoating.Core.Entities;
 public class JobTimeEntry : BaseEntity
 {
     public int JobId { get; set; }
-    public int ShopWorkerId { get; set; }
+    public int? ShopWorkerId { get; set; }       // legacy — kept for entries created before user migration
+    public string? UserId { get; set; }           // FK to AspNetUsers
+    public string? UserDisplayName { get; set; }  // snapshot of worker name at entry creation time
     public DateTime WorkDate { get; set; }
     public decimal HoursWorked { get; set; }
     public string? Stage { get; set; }   // e.g. "Sandblasting", "Coating", "Masking" — free text
@@ -11,5 +13,5 @@ public class JobTimeEntry : BaseEntity
 
     // Navigation
     public virtual Job Job { get; set; } = null!;
-    public virtual ShopWorker Worker { get; set; } = null!;
+    public virtual ShopWorker? Worker { get; set; }  // nullable — only populated for legacy entries
 }

src/PowderCoating.Core/Entities/PlatformSettingKeys.cs

@@ -15,4 +15,6 @@ public static class PlatformSettingKeys
     public const string MaxTenants                 = "MaxTenants";
     public const string SmsEnabled                 = "SmsEnabled";
     public const string AiCatalogPriceCheckEnabled = "AiCatalogPriceCheckEnabled";
+    public const string GracePeriodDays             = "GracePeriodDays";
+    public const string GracePeriodAppliesToTrials  = "GracePeriodAppliesToTrials";
 }