LLM Providers (#52)

* Refactor configs dei modelli
* Aggiunti Providers
* Update .env.example
* Xai Aggiunto ma commentato (problemi di dependency)

.env.example

@@ -5,6 +5,15 @@
 # https://makersuite.google.com/app/apikey
 GOOGLE_API_KEY=
 
+# https://platform.openai.com/settings/organization/api-keys
+OPENAI_API_KEY=
+
+# https://admin.mistral.ai/organization/api-keys
+MISTRAL_API_KEY=
+
+# https://platform.deepseek.com/api_keys
+DEEPSEEK_API_KEY=
+
 
 ###############################################################################
 # Configurazioni per gli agenti di mercato