[Feature] [Azure] Implement Full Azure OpenAI Support (UI + Backend)

[HexdoAI]

**Parent Epic: #56 **

🎯 Goal

Implement end-to-end support for the Azure OpenAI Service.

💻 UI Requirements (Frontend)

1. On the "Add Custom Model" page, add a "Provider Type" dropdown menu.
2. This menu should include "OpenAI" (default) and "Azure OpenAI" as options.
3. When a user selects "Azure OpenAI", the form must show the following required fields:
   • Endpoint (or Base URL): e.g., https://my-resource.openai.azure.com
   • API address
   • API Version: e.g., 2024-05-01-preview

⚙️ Backend Requirements

1. Modify the "save model" API to store the new provider_type and the associated Azure-specific fields.
2. Modify the logic in llm.azure.openai.js (or related files) to ensure it correctly receives these 4 parameters from the configuration.
3. The request URL must be constructed correctly using these parameters, following this format:
   [Endpoint]/openai/deployments/[Deployment ID]/chat/completions?api-version=[API Version]

✅ Acceptance Criteria

• A user can successfully add and save an Azure configuration via the UI.
• The system can use this configuration to successfully call the Azure OpenAI API.
• This task will resolve the TypeError: Invalid URL error reported in the parent Epic's logs.