v9.5: 實作標籤完全不重疊算法

- 新增 _calculate_lane_conflicts_v2() 分開返回標籤重疊和線穿框分數
- 修改泳道選擇算法，優先選擇無標籤重疊的泳道
- 兩階段搜尋：優先側別無可用泳道則嘗試另一側
- 增強日誌輸出，顯示標籤範圍和詳細衝突分數

🤖 Generated with Claude Code
Co-Authored-By: Claude <noreply@anthropic.com>

tests/integration/conftest.py

@@ -0,0 +1,31 @@
+"""
+整合測試配置
+
+提供 FastAPI 測試客戶端和通用 fixtures
+"""
+
+import pytest
+import pytest_asyncio
+from httpx import AsyncClient, ASGITransport
+from backend.main import app
+
+@pytest_asyncio.fixture
+async def client():
+    """
+    AsyncClient fixture for testing FastAPI endpoints
+
+    使用 httpx.AsyncClient 來測試 async 端點
+    """
+    transport = ASGITransport(app=app)
+    async with AsyncClient(transport=transport, base_url="http://test") as ac:
+        yield ac
+
+
+@pytest.fixture
+def sample_csv_content():
+    """範例 CSV 內容"""
+    return b"""id,title,start,end,group,description,color
+evt-001,Event 1,2024-01-01,2024-01-02,Group A,Test event 1,#3B82F6
+evt-002,Event 2,2024-01-05,2024-01-06,Group B,Test event 2,#10B981
+evt-003,Event 3,2024-01-10,,Group A,Test event 3,#F59E0B
+"""