Add Native Support for Opper.ai Provider

Hello TypingMind Team,

I would like to request the inclusion of Opper.ai as a native AI provider in the model settings, alongside OpenAI, Anthropic, OpenRouter, etc.

Why this would be a great addition:

- European-focused and GDPR-compliant: Opper.ai hosts and processes data in Europe, which is highly requested by enterprise and privacy-conscious users.

- OpenAI-compatible API: Since their API already mimics OpenAI's structure, integration should be relatively straightforward.

- Advanced orchestration: Opper offers great features for structured outputs and long-term memory that many of us are starting to use in our workflows.

While it is currently possible to add it via the Custom Model option, having native support with automatic model fetching, proper iconography, and official token tracking would greatly improve the user experience.

Thank you for considering this request!