fix: drop unexpected market_type kwarg at LiveOrderPhaseAdapter call site

[z20251130]

Summary

Strategy-generated live orders crash at final placement with TypeError: LiveOrderPhaseAdapter.__init__() got an unexpected keyword argument 'market_type', so every live auto-order (all exchanges, spot and swap) has failed since d169c03 (2026-08-27). The commit added market_type= to the LiveOrderPhaseAdapter(...) call, but the class never accepted that parameter. This PR removes the stray kwarg.

Root cause

• d169c03 ("refactor: unify exchange instrument rules") modified the call site in pending_order_worker.py but not the adapter class (live_trading/adapters.py, last changed 2026-07-22).
• The adapter takes market_type from the OrderIntent in every method (place_market_order / place_limit_order / cancel_order / wait_for_fill), so the kwarg was not only unexpected but also unused — removing it from the call site is behavior-preserving.
• No test covers this call site (test_live_exchange_fees.py constructs the adapter without the kwarg), and the failure path is only reachable through live auto-trading, which is why it went unnoticed.

Observed in production logs:

Unexpected order error (binance BNB/USDT open_long): LiveOrderPhaseAdapter.__init__() got an unexpected keyword argument 'market_type'

Changes

• backend_api_python/app/services/pending_order_worker.py: remove the single unexpected market_type=market_type, line from the LiveOrderPhaseAdapter(...) call. 1 line, nothing else.

Test plan

• python -m py_compile backend_api_python/app/services/pending_order_worker.py
• Reproduced the TypeError on 21f1fb6 with the exact worker kwargs; confirmed the adapter constructs cleanly after removing the kwarg
• Deployed locally (docker image rebuilt): the previously crashing BNB/USDT open_short (swap) + open_long (spot) strategy orders now pass the placement phase and reach the exchange

API documentation

• No route/schema changes — no OpenAPI regeneration needed.

Backward compatibility

• Fully backward compatible; restores pre-d169c03 behavior.