feat: Implement real Mercado Pago API integration for payment preference creation and webhook processing, replacing mock calls and adding necessary environment variables.

.env.example

@@ -21,3 +21,11 @@ OPENAI_API_KEY=
 LOCAL_WHISPER_URL=http://t-800:9000
 LOCAL_OLLAMA_URL=http://t-800:11434
 LOCAL_LLM_MODEL=llama3.2:3b
+ 
+# Mercado Pago Configuration
+MP_ACCESS_TOKEN=
+MP_PUBLIC_KEY=
+MP_WEBHOOK_SECRET=
+MP_BACK_URL_SUCCESS=http://localhost:3003/payments/success
+MP_BACK_URL_FAILURE=http://localhost:3003/payments/failure
+MP_NOTIFICATION_URL=