backend phase 0: foundation, cross-cutting seams & starter cleanup

Remove the Order demo (entity/feature/repo/config/gRPC/proto) and the three
pre-marketplace migrations; regenerate a fresh InitialBaseline migration.

Stand up the REST surface (PingController + System/Ping CQRS) proving the
Mediator -> behaviors -> OperationResult -> ApiResult envelope end to end.

Close wiring gaps: register LoggingBehavior (outermost) and add the built-in
rate limiter (per-IP global + otp/auth/sensitive policies), placed before
authentication.

Add current-user + audit plumbing: ICurrentUser (HttpContext + null impls),
rename BaseEntity audit fields to CreatedAt/ModifiedAt (DateTimeOffset) +
CreatedById/ModifiedById, stamped by a new AuditFieldInterceptor.

Introduce five cross-cutting seams (IDateTimeProvider, IFieldEncryptor,
ICacheService, IObjectStorage, INotificationDispatcher) with in-memory/local
mocks registered via AddCrossCuttingSeams.

Add Baya.Test.Foundation (encryptor, audit interceptor, ping handler) and
update docs, contracts (swagger.v1.json), handoff, report, and mocks registry.

server/src/Core/Baya.Domain/Common/BaseEntity.cs

@@ -1,4 +1,4 @@
-namespace Baya.Domain.Common;
+namespace Baya.Domain.Common;
 
 public interface IEntity
 {
@@ -6,11 +6,21 @@ public interface IEntity
 
 public interface ITimeModification
 {
-    DateTime CreatedTime { get; set; }
-    DateTime? ModifiedDate { get; set; }
+    DateTimeOffset CreatedAt { get; set; }
+    DateTimeOffset? ModifiedAt { get; set; }
 }
 
-public abstract class BaseEntity<TKey> : IEntity, ITimeModification
+/// <summary>
+/// An entity whose create/modify timestamps and the acting user are stamped automatically by the
+/// SaveChanges audit interceptor — handlers must never set these fields themselves.
+/// </summary>
+public interface IAuditableEntity : ITimeModification
+{
+    int? CreatedById { get; set; }
+    int? ModifiedById { get; set; }
+}
+
+public abstract class BaseEntity<TKey> : IEntity, IAuditableEntity
 {
     public TKey Id { get; protected set; }
 
@@ -49,11 +59,13 @@ public abstract class BaseEntity<TKey> : IEntity, ITimeModification
         return (GetType().ToString() + Id).GetHashCode();
     }
 
-    public DateTime CreatedTime { get; set; }
-    public DateTime? ModifiedDate { get; set; }
+    public DateTimeOffset CreatedAt { get; set; }
+    public DateTimeOffset? ModifiedAt { get; set; }
+    public int? CreatedById { get; set; }
+    public int? ModifiedById { get; set; }
 }
 
 public abstract class BaseEntity : BaseEntity<int>
 {
 
-}
+}

server/src/Core/Baya.Domain/Entities/Order/Order.cs

@@ -1,16 +0,0 @@
-using Baya.Domain.Common;
-
-namespace Baya.Domain.Entities.Order;
-
-public class Order:BaseEntity
-{
-    public string OrderName { get; set; }
-    public bool IsDeleted { get; set; }
-
-    #region Navigation Properties
-
-    public User.User User { get; set; }
-    public int UserId { get; set; }
-
-    #endregion
-}

server/src/Core/Baya.Domain/Entities/User/User.cs

@@ -19,11 +19,4 @@ public class User:IdentityUser<int>,IEntity
     public ICollection<UserClaim> Claims { get; set; }
     public ICollection<UserToken> Tokens { get; set; }
     public ICollection<UserRefreshToken> UserRefreshTokens { get; set; }
-
-    #region Navigation Properties
-
-    public IList<Order.Order> Orders { get; set; }
-
-    #endregion
-
 }

server/src/Core/Baya.Domain/Entities/User/UserRefreshToken.cs

@@ -1,16 +1,10 @@
-using Baya.Domain.Common;
+using Baya.Domain.Common;
 
 namespace Baya.Domain.Entities.User;
 
 public class UserRefreshToken:BaseEntity<Guid>
 {
-    public UserRefreshToken()
-    {
-        CreatedAt=DateTime.Now;
-    }
-
     public int UserId { get; set; }
     public User User { get; set; }
-    public DateTime CreatedAt { get; set; }
     public bool IsValid { get; set; }
-}
+}