fix: use current_price for overseas limit orders (KIS VTS rejects market orders) (#149)

KIS VTS (paper trading) rejects overseas market orders with:
  "모의투자 주문처리가 안되었습니다(지정가만 가능한 상품입니다)"

Root cause: send_overseas_order() was called with price=0.0 (market order)
in both trading_cycle() and run_daily_session(), even though current_price
was already computed correctly by Fix #147 (exchange code mapping).

Fix: pass current_price as the limit order price in both call sites.
Domestic broker send_order() keeps price=0 (market orders are fine on KRX).

Adds regression test TestOverseasBalanceParsing::test_overseas_buy_order_uses_limit_price
verifying price=182.5 is passed, not 0.0.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/main.py

@@ -510,7 +510,7 @@ async def trading_cycle(
                 stock_code=stock_code,
                 order_type=decision.action,
                 quantity=quantity,
-                price=0.0,  # market order
+                price=current_price,  # limit order — KIS VTS rejects market orders
             )
         logger.info("Order result: %s", result.get("msg1", "OK"))
 
@@ -919,7 +919,7 @@ async def run_daily_session(
                             stock_code=stock_code,
                             order_type=decision.action,
                             quantity=quantity,
-                            price=0.0,  # market order
+                            price=stock_data["current_price"],  # limit order — KIS VTS rejects market orders
                         )
                     logger.info("Order result: %s", result.get("msg1", "OK"))