feat: add optional structured market sentiment tool for QueryAgent

[alexander-schneider]

Summary

This PR adds an optional structured market sentiment research path to QueryAgent.

It includes:

• an optional search_market_sentiment tool backed by Adanos
• a small fix so QueryEngine actually preserves search_tool, start_date, and end_date from the LLM output
• config and UI wiring for an optional ADANOS_API_KEY
• tests covering prompt toggles, tool selection preservation, fail-open behavior, structured result formatting, and date-range normalization

Why this shape

I kept the integration intentionally narrow:

• no changes to MindSpider, InsightEngine, or ReportEngine
• no change to the default public-opinion workflow
• no requests unless ADANOS_API_KEY is configured

The new tool adapts Adanos stock and market sentiment responses into the existing SearchResult/TavilyResponse shape, so the current summary and report pipeline can reuse it without a separate downstream format.

Notes

• Without ADANOS_API_KEY, the default behavior is unchanged.
• The result links point to the public Adanos docs instead of protected API endpoints.
• The QueryAgent prompt only advertises the structured market sentiment tool when the optional key is configured.

Validation

• python3 -m pytest tests/test_query_engine_market_sentiment.py -q
• python3 -m pytest tests/ -q
• python3 -m py_compile QueryEngine/agent.py QueryEngine/nodes/search_node.py QueryEngine/tools/market_sentiment.py QueryEngine/prompts/prompts.py QueryEngine/utils/config.py app.py config.py
• git diff --check