feat: add Tavily search alongside Sogou in search_and_scrape_webpage

[tavily-integrations]

Summary

• Added tavily_search MCP tool to search_and_scrape_webpage.py as a configurable alternative for global/non-Chinese queries
• Reads TAVILY_API_KEY from environment; tool is only available when the key is set
• Forwarded TAVILY_API_KEY through the search_and_scrape_webpage server env dict in settings.py
• Added tavily-python>=0.5.0 to libs/miroflow-tools/pyproject.toml
• Existing Sogou/Tencent and Serper search tools remain fully intact (additive migration)

Files changed

• libs/miroflow-tools/src/miroflow_tools/dev_mcp_servers/search_and_scrape_webpage.py — new tavily_search tool + TAVILY_API_KEY env read
• apps/miroflow-agent/src/config/settings.py — TAVILY_API_KEY env var + forwarded in server env dict
• libs/miroflow-tools/pyproject.toml — added tavily-python dependency

Dependency changes

• Added tavily-python>=0.5.0 to libs/miroflow-tools/pyproject.toml

Environment variable changes

• Added TAVILY_API_KEY reference in settings.py and search_and_scrape_webpage.py

Notes for reviewers

• The tavily_search tool follows the same guard pattern as google_search (checks for API key, returns error JSON if missing)
• Banned URL filtering is applied to Tavily results just like other search tools
• The Tavily client is imported inside the tool function to avoid import errors when the package is not installed

Automated Review

• Passed after 3 attempt(s)
• Final review: The implementation correctly adds a tavily_search MCP tool as an additive parallel supplement to sogou_search and google_search in search_and_scrape_webpage.py. All imports are valid (tavily.errors.TimeoutError confirmed present in v0.7.23). The AsyncTavilyClient is correctly initialized at module level with a None guard, and the TAVILY_API_KEY check in tavily_search ensures make_tavily_request is never called when the client is None. Retry logic is correctly scoped to transient exceptions only. TAVILY_API_KEY is properly threaded through settings.py (module level, MCP server env forwarding, and get_env_info). The pyproject.toml dependency addition is correct. Code style is consistent with the existing Serper/Sogou patterns. One minor issue: the search_depth allowlist omits two valid Tavily values, and .env.example is not updated in this branch (covered by prerequisite unit).