feat: source CN equity and futures bars from Ricequant

[Jason55-1118]

Summary

Route A-share, HK, and CN futures research K-lines through Ricequant RQData, vendor ricequant-skills, and persist bars under DATE/ for local reuse.

Changes

• Install ricequant-skills under .cursor/skills/ plus a QuantDinger RQData routing skill
• Prefer rqdatac.get_price for CNStock / HKStock / CN futures (rqdata_equity.py, rqdata_futures.py)
• Add host DATE/ CSV archive with factory read/write-back and scripts/download_date_history.py
• Wire CN_STOCK_PROVIDER / HK_STOCK_PROVIDER / FUTURES_CN_PROVIDER and DATE bind mounts in compose / env.example

Test plan

• python -m pytest tests/test_rqdata_equity.py tests/test_rqdata_futures.py tests/test_local_archive.py -q (12 passed)
• Downloaded 36 CN stock/futures 1D series via RQData into DATE/
• Tested locally with docker compose up -d --build
• Backend logs show no errors
• Relevant pytest tests pass

API documentation (if routes/schemas changed)

• Regenerated docs/api/openapi.yaml (cd backend_api_python && python scripts/export_openapi.py)
• Updated docs/agent/agent-openapi.json if /api/agent/v1 routes changed
• Breaking API changes called out below (oasdiff will fail CI otherwise)

No human or Agent HTTP routes/schemas changed.

Screenshots (if UI change)

N/A