Added Requesty as a provider

Requesty is an OpenAI compatible AI gateway. The provider mirrors OpenRouter: chat completions over https://router.requesty.ai/v1/, the same project headers, and a model list read from both the managed policies (models/managed) and the full catalog (models), including the context window.

app/MindWork AI Studio/Provider/Requesty/RequestyModelsResponse.cs

@@ -0,0 +1,7 @@
+namespace AIStudio.Provider.Requesty;
+
+/// <summary>
+/// A data model for the response from the Requesty models endpoints.
+/// </summary>
+/// <param name="Data">The list of models.</param>
+public readonly record struct RequestyModelsResponse(IList<RequestyModel> Data);