feat: 项目流水拆分为确收与回款+费用明细两Tab + 数据迁移

后端:
- 新增 expense_data TEXT 列(columns.py迁移)
- 新增 data_split 迁移:旧 budget_data cost/paid → expense_data(幂等)
- sum_budget cost/paid → sum_expense cost/paid(routes.py/helpers.py)
- TABLES 配置加入 expense_data

前端:
- 项目详情弹窗Tab:基本信息→确收与回款→费用明细→执行信息→任务管理→活动
- 确收与回款Tab:月份/确收/毛利/回款/备注
- 费用明细Tab:月份/费用类型/应付/已付/备注
- 项目表格三视图(月/季/总)cost/paid来源切换为expense_data
- 保存逻辑分两路: budget_data(rev/gross/payment)+expense_data(cost/paid)

backend/migrations/data_split.py

@@ -0,0 +1,56 @@
+"""migrations/data_split.py — 预算数据拆分迁移：budget_data → expense_data
+
+旧结构：budget_data = [{month, rev, gross, payment, cost, paid}]
+新结构：expense_data = [{month, expense_type, cost, paid, exp_note}]
+
+部署时自动：检测未拆分的旧数据，将 cost/paid 从 budget_data 迁移到 expense_data。
+幂等：只处理 expense_data 为空的记录。
+"""
+
+
+def migrate_data_split():
+    """一次性数据拆分迁移"""
+    from db import db, _exec
+    import json
+
+    conn = db()
+    try:
+        # 查询未迁移的记录
+        cur = conn.cursor(dictionary=True)
+        cur.execute(
+            "SELECT id, budget_data, expense_data FROM project_finances "
+            "WHERE (expense_data IS NULL OR expense_data = '' OR expense_data = '[]') "
+            "AND budget_data IS NOT NULL AND budget_data != '' AND budget_data != '[]'"
+        )
+        rows = cur.fetchall()
+        cur.close()
+
+        migrated = 0
+        for row in rows:
+            try:
+                budget = json.loads(row.get("budget_data") or "[]")
+            except (json.JSONDecodeError, TypeError):
+                continue
+
+            expense_rows = []
+            for b in budget:
+                expense_rows.append({
+                    "month": b.get("month", ""),
+                    "expense_type": "",
+                    "cost": float(b.get("cost") or 0),
+                    "paid": float(b.get("paid") or 0),
+                    "exp_note": "",
+                })
+
+            if expense_rows:
+                _exec(
+                    conn,
+                    "UPDATE project_finances SET expense_data = ? WHERE id = ?",
+                    (json.dumps(expense_rows, ensure_ascii=False), row["id"]),
+                )
+                migrated += 1
+
+        conn.commit()
+        print(f"[migrate] 数据拆分迁移完成：{migrated} 条记录已从 budget_data 提取 cost/paid 到 expense_data")
+    finally:
+        conn.close()