fix(formula): 导出文件安全、清理回收、撤权校验与定义库可靠性（F01/F02/F05-F08）

- F01: _safe_unlink_export 不跟随符号链接、逐层校验父目录，导出失败路径与
  清理命令统一使用，只清理受控目录内本次创建的文件
- F02: 清理失败记录告警日志；清理命令回收 failed 任务残留文件
- F05: 定义保存事务内锁数据集行，配额原子检查；revision 冲突返回 409；
  保留最近 20 版历史；支持个人/团队共享；审计与变更同事务
- F06: 工作簿参数页毛利率改为只读快照；可编辑单元格解锁并加数值校验
- F07: 对账按指标分容差（人数 0、比率 0.0001、金额 0.01）；自定义列使用
  服务端 Decimal 表达式求值参考
- F08: 导出任务执行/下载阶段重校验账号有效性与角色
- 对话草稿会话恢复；载入定义后追问携带原定义（F04）；下载改浏览器直传
- 迁移 0006-0008；PostgreSQL 咨询锁语义修正（import_worker）

tests/test_formula_columns.py

@@ -97,8 +97,30 @@ def test_formula_workbook_exposes_custom_metric_as_recalculable_column(formula_d
     custom = workbook["自定义指标"]
     assert custom["B1"].value == "收入成本差（本期）"
     assert custom["B2"].value == f"='分析汇总'!C{metric_row}"
-    assert "含义：实际收入减成本" in workbook["使用说明"]["B12"].value
-    assert "范围：按所选分组及本期、基期计算" in workbook["使用说明"]["B12"].value
+    instruction_text = " ".join(str(cell.value) for row in workbook["使用说明"].iter_rows() for cell in row)
+    assert "含义：实际收入减成本" in instruction_text
+    assert "范围：按所选分组及本期、基期计算" in instruction_text
+
+
+def test_formula_workbook_protects_structure_and_unlocks_calculation_inputs(formula_data):
+    ds, member = formula_data
+    output = BytesIO()
+    build_formula_workbook(
+        ds,
+        member,
+        {"start": "2026-08", "end": "2026-08", "comparison": "yoy", "group": "department"},
+        output,
+    )
+    workbook = load_workbook(BytesIO(output.getvalue()), data_only=False)
+    data = workbook["计算明细"]
+    assert data.protection.sheet
+    assert data["D2"].protection.locked is False
+    assert data["F2"].protection.locked is False
+    assert data["G2"].protection.locked is False
+    assert data["I2"].protection.locked is False
+    assert data["C2"].protection.locked is True
+    assert data["M2"].protection.locked is True
+    assert workbook["原始证据"].protection.sheet
 
 
 def test_custom_expression_rejects_formula_text_and_unknown_metrics():