Azure OpenAI Service (2026-04-01)

Migrated to the chat completions API with updated defaults, configuration, and model selection:

• Migrated completions actions to the chat completions API
• Updated default model from gpt-3.5-turbo-instruct to gpt-4o-mini
• Added configurable API Version connection field
• Added Select Model data source for model dropdown selection
• Added model input to Create Image action (replacing hardcoded dalle-3)
• Updated response payload field names