Fix exchange API errors: stop cascade BUY failures and stop-loss race condition

- Set available_usdt=0 after BUY fails with "not enough balance" to prevent
  subsequent BUY signals from hitting the exchange in the same cycle
- Add 0.3s delay after canceling stop orders before placing new ones to let
  Bitfinex release locked balance

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

main.py

@@ -149,6 +149,7 @@ def run_cycle():
                 logger.info("Cancelled outdated stop %s for %s (amt=%.6f, px=%.6g)",
                             s["id"], sym, abs(s["amount"]), s["price"])
             tracked_stops.pop(sym, None)
+            time.sleep(0.3)  # Wait for Bitfinex to release locked balance
 
         logger.warning("Position %s missing/outdated stop-loss, placing now", sym)
         sl = trader.place_stop_loss_order(sym, amount, entry)
@@ -345,6 +346,10 @@ def run_cycle():
         if result and result.get("status") == "failed":
             logger.warning("Order failed at exchange: %s %s — %s", action, validated["symbol"], result.get("error", ""))
             rejected.append({**validated, "reject_reason": f"交易所錯誤: {result.get('error', 'unknown')}"})
+            # BUY failed at exchange — mark balance as unreliable to skip remaining BUYs
+            if action == "BUY" and "not enough" in result.get("error", "").lower():
+                port["available_usdt"] = 0
+                logger.info("Marked available_usdt=0 to prevent further BUY attempts this cycle")
             continue
 
         if result and result.get("status") in ("filled", "submitted"):
@@ -369,9 +374,13 @@ def run_cycle():
             if action == "BUY":
                 # Cancel existing exchange stop orders before placing new one
                 pos = port.get("positions", {}).get(sym, {})
+                cancelled_any = False
                 for s in stop_orders_by_sym.get(sym, []):
                     trader.cancel_order(s["id"])
+                    cancelled_any = True
                     logger.info("Cancelled old stop %s for %s (position size changed)", s["id"], sym)
+                if cancelled_any:
+                    time.sleep(0.3)  # Wait for Bitfinex to release locked balance
 
                 # Place new stop-loss for TOTAL position amount at new avg entry
                 total_amount = pos.get("amount", amount)