68ae4b7bee
- Added Tavily web search provider with API key authentication and credential discovery from environment or database. - Integrated Tavily as highest-priority search provider in fallback chain with structured response mapping and error handling. - Added Tavily OAuth login flow in CLI and auth-storage with manual API key input and validation. - Added comprehensive test suite for Tavily provider covering registration, response mapping, error handling, and credential validation. Fixes #313