docs(openapi): regenerate docs/api/openapi.yaml to match current routes and schemas

[huuan26]

Summary

Regenerates docs/api/openapi.yaml via python scripts/export_openapi.py so the committed OpenAPI specification matches the current Flask-Smorest route and schema definitions on main (following recent refactors and endpoint additions in 437b01e and 13f2bca), resolving the OpenAPI CI drift failure (docs/api/openapi.yaml is out of date).

Related issue

• Fixes OpenAPI CI failure on main (run #39092211864)

Changes

• docs/api/openapi.yaml:
  • Remove obsolete ai_decision_filter field from StrategyCreateRequest schema (removed in 13f2bca).
  • Add /api/backtest/jobs, /api/backtest/jobs/{job_id}, and /api/backtest/jobs/{job_id}/cancel internal strategy endpoints.
  • Add /api/indicator/preview-image and /api/indicator/preview-images/{filename} indicator preview endpoints.
  • Sync updated docstrings for postApiIndicatorCodeQualityHints (runtimeCheck parameter) and QuickTrade (tp_price / sl_price descriptions).

Test plan

• Exported spec matches python scripts/export_openapi.py output with zero diff
• Relevant pytest tests pass (pytest backend_api_python/tests/test_openapi.py)

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 (no /api/agent/v1 changes)
• Breaking API changes called out below: ai_decision_filter was already removed from StrategyCreateRequest in 13f2bca