add architecture skeleton

GymLogAI.Core/Abstractions/IClock.cs

@@ -0,0 +1,6 @@
+namespace GymLogAI.Core.Abstractions;
+
+public interface IClock
+{
+    DateTime UtcNow { get; }
+}

GymLogAI.Core/Abstractions/IIdGenerator.cs

@@ -0,0 +1,6 @@
+namespace GymLogAI.Core.Abstractions;
+
+public interface IIdGenerator
+{
+    Guid New();
+}