Adds self-hosted Google Search Console support, plus a few setup and error-message fixes.

## What's new

- Connect Google Search Console in self-hosted OpenSEO with your own Google OAuth client.
- Use the new Search Console MCP tools for performance data and URL inspection from your own GSC account.

## Improved

- Temporary DataForSEO 5xx errors now get quick retries and a clearer "temporarily unavailable" message.

## Fixed

- Invalid domains now fail earlier with a clearer "enter a valid domain" message.

Full Changelog: https://github.com/every-app/open-seo/compare/v0.0.17...v0.0.18