chore: add reset_data.py for clearing demo data before production use

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/reset_data.py

@@ -0,0 +1,39 @@
+"""清除所有业务数据，保留用户和角色
+用途：正式启用前清除演示数据
+"""
+from database import SessionLocal
+from models import (
+    SubmissionHistory, Submission, OutsourceCost, CostOverride,
+    AIToolCostAllocation, AIToolCost, OverheadCost, ProjectMilestone, Project
+)
+
+db = SessionLocal()
+
+tables = [
+    ("提交历史", SubmissionHistory),
+    ("内容提交", Submission),
+    ("外包成本", OutsourceCost),
+    ("人力调整", CostOverride),
+    ("AI工具分摊", AIToolCostAllocation),
+    ("AI工具成本", AIToolCost),
+    ("固定开支", OverheadCost),
+    ("项目里程碑", ProjectMilestone),
+    ("项目", Project),
+]
+
+print("即将清除以下数据（用户和角色不受影响）：")
+for label, model in tables:
+    count = db.query(model).count()
+    print(f"  {label}: {count} 条")
+
+confirm = input("\n确认清除？输入 yes 继续: ")
+if confirm.strip().lower() != "yes":
+    print("已取消")
+    exit()
+
+for label, model in tables:
+    deleted = db.query(model).delete()
+    print(f"  已删除 {label}: {deleted} 条")
+
+db.commit()
+print("\n✓ 所有业务数据已清除，用户和角色保留。系统已准备好正式使用。")