add architecture skeleton

GymLogAI.Application/Interfaces/IWorkoutRecommendationGenerator.cs

@@ -0,0 +1,12 @@
+using GymLogAI.Application.DTOs;
+using GymLogAI.Core.Entities;
+
+namespace GymLogAI.Application.Interfaces;
+
+public interface IWorkoutRecommendationGenerator
+{
+    Task<WorkoutRecommendationDto> GenerateAsync(
+        WorkoutRecommendationContext context,
+        IReadOnlyCollection<Workout> workoutHistory,
+        CancellationToken cancellationToken);
+}