feat: 在方案对比表格中增加损耗费用净现值列

- 新增'损耗费用净现值 (万元)'列，显示生命周期内损耗费用的净现值
- 使用npv_loss字段替代annual_loss_cost，考虑折现率对全生命周期成本的影响
- 支持按损耗费用净现值排序，便于方案经济性对比

gui.py

@@ -815,6 +815,7 @@ def index():
                         "cost_wan": f"{res['cost'] / 10000:.2f}",
                         "loss_kw": f"{res['loss']:.2f}",
                         "total_length": f"{total_length_km:.2f}",
+                        "npv_loss_wan": f"{res.get('npv_loss', 0) / 10000:.2f}",
                         "total_cost_npv_wan": f"{res.get('total_cost_npv', res['cost']) / 10000:.2f}",
                         "note": note,
                         "original_name": res["name"],
@@ -984,6 +985,12 @@ def index():
                             "field": "total_length",
                             "sortable": True,
                         },
+                        {
+                            "name": "npv_loss_wan",
+                            "label": "损耗费用净现值 (万元)",
+                            "field": "npv_loss_wan",
+                            "sortable": True,
+                        },
                         {
                             "name": "total_cost_npv_wan",
                             "label": "总费用 (万元)",