Add skill to connect to Alexa using Azure Foundry (backend & frontend)

[Javierif]

Implement a new skill to enable integration between AzulClaw and Alexa using Azure Foundry, anticipating the deprecation of Azure Bot Framework.

The implementation must cover:

• Backend logic for secure communication with Alexa via Azure Foundry
• UI configuration in both the initial setup wizard and the skills tab
• Allow management and setup of the Alexa integration from the frontend
• Document authentication/API requirements and user flows

This will allow users to securely connect their AzulClaw assistants to Alexa while leveraging modern Azure infrastructure.