Feature request: Add CometAPI as an LLM provider

[TensorNull]

Is your feature request related to a problem? Please describe.
Perplexica users often need more provider redundancy, regional coverage, and pricing flexibility for production workloads. Relying on a limited set of providers can lead to outages under rate limits, regional unavailability, or budget constraints. Adding CometAPI (OpenAI-compatible) would improve reliability and cost control while preserving existing UX and APIs.

Describe the solution you'd like

• Add CometAPI as a first-class LLM provider in Perplexica, or enable configuring the existing OpenAI client with a baseURL to target CometAPI.
• Support core features:
  • Chat and text generation via OpenAI-compatible endpoints
  • Model listing and selection via CometAPI model APIs
  • API key configuration and secure secret handling
  • Streaming and non-streaming responses if Perplexica supports both modes
• Provide a minimal example and documentation for using CometAPI within Perplexica (env vars, model selection, streaming toggle, etc.).

Describe alternatives you've considered

• Using current OpenAI integration with a custom baseURL. This works but is not obvious to users and may cause subtle compatibility gaps or support questions.
• Using third-party proxies/aggregators. Adds an extra moving part and less control.
• Staying on current providers only. Reduces resilience and flexibility during spikes or outages.

Additional context
CometAPI Resources:

• Website: https://www.cometapi.com/
• API Documentation: https://api.cometapi.com/doc
• Base URL: https://api.cometapi.com/v1/
• Model List: https://api.cometapi.com/v1/models
• Get API Key: https://api.cometapi.com/console/token
• Pricing: https://api.cometapi.com/pricing

Compatibility:

• CometAPI provides OpenAI-compatible endpoints, so integration should be low-friction if Perplexica already abstracts providers behind a common interface.

Implementation Offer:

• We’re happy to submit a PR following your contribution guidelines (with examples and docs). We can also supply a temporary test API key and a demo to validate functionality. Please advise on the preferred integration path and acceptance criteria.