feat: Add OpenRouter as third LLM provider

[becker-charles]

Summary

Adds OpenRouter as a third LLM provider alongside Claude and Gemini, providing access to GPT-5.3, GPT-4o Mini, Claude Sonnet/Opus 4.x, and Grok 4.3 via OpenRouter's unified API.

Changes

Backend:

• New openrouter.ts streaming implementation using OpenAI-compatible API
• Added provider type and model definitions
• Routes OpenRouter calls in LLM index
• Includes openrouter_api_key in user settings queries

Frontend:

• Added OpenRouter models to ModelToggle
• Added OpenRouter API key input in Account → Models
• Updated model availability checks

Database:

• Migration 001_add_openrouter_api_key.sql for existing deployments
• Updated one-shot schema for fresh deployments

Models Added

• GPT-5.3
• GPT-4o Mini
• Claude Sonnet 4.6 (via OpenRouter)
• Claude Opus 4.7 (via OpenRouter)
• Grok 4.3

Test Plan (Fully Completed, Passed)

• Run migration
• Add OpenRouter API key in Account → Models
• Select OpenRouter model in chat
• Verify streaming works

[becker-charles]

@willchen96 could not find contributors file. perhaps worth standardizing a format.

great project, nonetheless!

[willchen96]

Thanks Charles for the suggestion and for putting this together.

I’m going to hold off on merging OpenRouter support for now because the main branch has changed significantly due to recent security updates, especially around API key handling, backend-owned data access, and model/provider configuration. I don’t want to merge provider changes on top of an older structure and risk reintroducing inconsistencies.

OpenRouter support is still something I’d like to add later, but I’d prefer to do it against the updated provider/key architecture so it fits cleanly with the current model settings and security model.

Closing this for now, but I appreciate the contribution.