* Extended functionalities

* Added different UIs

MealPlan.Api/Services/AI/OpenAiOptions.cs

@@ -0,0 +1,44 @@
+namespace MealPlan.Api.Services.AI;
+
+public enum OpenAiUseCase
+{
+    Default,
+    Macros,
+    Plan,
+    Recipe,
+}
+
+public class OpenAiOptions
+{
+    public const string SectionName = "OpenAI";
+
+    public string ApiKey { get; set; } = string.Empty;
+
+    /// <summary>Fallback when a task-specific model is not set.</summary>
+    public string Model { get; set; } = "gpt-4.1-mini";
+
+    /// <summary>Macro target refinement (diet generator step 2).</summary>
+    public string? MacrosModel { get; set; }
+
+    /// <summary>Weekly meal plan recipe selection (diet generator step 3).</summary>
+    public string? PlanModel { get; set; }
+
+    /// <summary>AI recipe draft generation and partial regen.</summary>
+    public string? RecipeModel { get; set; }
+
+    public int MaxTokens { get; set; } = 4096;
+
+    public bool IsConfigured => !string.IsNullOrWhiteSpace(ApiKey);
+
+    public string ResolveModel(OpenAiUseCase useCase) =>
+        useCase switch
+        {
+            OpenAiUseCase.Macros => FirstNonEmpty(MacrosModel, Model),
+            OpenAiUseCase.Plan => FirstNonEmpty(PlanModel, Model),
+            OpenAiUseCase.Recipe => FirstNonEmpty(RecipeModel, Model),
+            _ => Model,
+        };
+
+    private static string FirstNonEmpty(string? preferred, string fallback) =>
+        string.IsNullOrWhiteSpace(preferred) ? fallback : preferred;
+}