fix: expose v2 search fields

[zxyasfas]

Summary

Expose the remaining documented /v2/search options through the firecrawl_search MCP tool and forward them to the Firecrawl API.

Changes

• Add categories, country, timeout, and ignoreInvalidURLs to the search tool schema.
• Accept both string and object forms for sources and categories, matching the public search request shape.
• Send search requests to /v2/search directly so accepted MCP fields are included in the API payload.
• Preserve the existing includeDomains / excludeDomains query-operator behavior before the API call.

Fixes #219.

Validation

• npm run build
• git diff --check -- src/index.ts