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/LLMProviders.cs

@@ -19,6 +19,7 @@ public enum LLMProviders
     HETZNER = 16,
     IONOS = 17,
     LITE_LLM = 18,
+    REQUESTY = 19,
 
     FIREWORKS = 5,
     GROQ = 6,