feat(analysis): 网页汇总表自定义列

- analyze 支持 custom_columns：白名单表达式树由服务端 Decimal 求值，
  自定义列进入汇总、分组行与明细（缺失保持不可用，不转零）
- 新增「选择网页自定义列」弹窗：从定义库（含共享）多选最多 10 列，
  应用后进入主分析表格与热力图；公式工作簿可一键导出网页已选列
- 请求去重纳入自定义列；Playwright 覆盖选择后显示与数值断言

tests/test_finance.py

@@ -85,6 +85,36 @@ def test_metrics_and_analysis_preserve_roi_refunds_and_distinct_customers(worksp
     assert unavailable["self_revenue"] == 0
 
 
+def test_analysis_computes_saved_custom_columns_in_summary_and_rows(workspace):
+    ds, member, *_ = workspace
+    column = {
+        "name": "收入成本差",
+        "meaning": "收入减成本",
+        "scope": "按分组计算",
+        "missing": "结果不可用（#N/A）；零分母不可用",
+        "expression": {
+            "operator": "subtract",
+            "left": {"metric": "revenue"},
+            "right": {"metric": "cost"},
+        },
+    }
+    result = analyze(
+        ds,
+        member,
+        {
+            "start": "2026-08",
+            "end": "2026-08",
+            "comparison": "yoy",
+            "group": "department",
+            "custom_columns": [column],
+        },
+        default_preferences(ds),
+    )
+    assert result["summary"]["custom_0"]["current"] == Decimal("45")
+    assert result["summary"]["custom_0"]["baseline"] == Decimal("90")
+    assert result["rows"][0]["values"]["custom_0"]["current"] == Decimal("60")
+
+
 def test_dataset_and_evidence_are_organization_and_department_scoped(workspace):
     ds, _, _, _, other_client = workspace
     url = f"/api/datasets/{ds.pk}"