fix: address code review round 2 — 9 issues (2 critical, 3 important, 4 minor)

Critical:
- #2: Add _entry_lock in RiskManager to serialize concurrent entry (balance race)
- #3: Add startTime to get_recent_income + record _entry_time_ms (SYNC PnL fix)

Important:
- #1: Add threading.Lock + _run_api() helper for thread-safe Client access
- #4: Convert reset_daily to async with lock
- #8: Add 24h TTL to exchange_info_cache

Minor:
- #7: Remove duplicate Indicators creation in _open_position (use ATR directly)
- #11: Add input validation for LEVERAGE, MARGIN ratios, ML_THRESHOLD
- #12: Replace hardcoded corr[0]/corr[1] with dict-based dynamic access
- #14: Add fillna(0.0) to LightGBM path for NaN consistency with ONNX

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

tests/test_config.py

@@ -48,3 +48,28 @@ def test_config_max_same_direction_default():
     """동일 방향 최대 수 기본값 2."""
     cfg = Config()
     assert cfg.max_same_direction == 2
+
+
+def test_config_rejects_zero_leverage():
+    """LEVERAGE=0은 ValueError."""
+    os.environ["LEVERAGE"] = "0"
+    with pytest.raises(ValueError, match="LEVERAGE"):
+        Config()
+    os.environ["LEVERAGE"] = "10"  # 복원
+
+
+def test_config_rejects_invalid_margin_ratio():
+    """MARGIN_MAX_RATIO가 0이면 ValueError."""
+    os.environ["MARGIN_MAX_RATIO"] = "0"
+    with pytest.raises(ValueError, match="MARGIN_MAX_RATIO"):
+        Config()
+    os.environ["MARGIN_MAX_RATIO"] = "0.50"  # 복원
+
+
+def test_config_rejects_min_gt_max_margin():
+    """MARGIN_MIN > MAX이면 ValueError."""
+    os.environ["MARGIN_MIN_RATIO"] = "0.80"
+    os.environ["MARGIN_MAX_RATIO"] = "0.50"
+    with pytest.raises(ValueError, match="MARGIN_MIN_RATIO"):
+        Config()
+    os.environ["MARGIN_MIN_RATIO"] = "0.20"  # 복원