后端第一步开发完成，第一版回归测试完成

backend/scripts/clean_db.py

@@ -0,0 +1,26 @@
+#!/usr/bin/env python3
+"""
+清空 projects 与 operation_logs 表（保留 users）。
+用法：cd backend && PYTHONPATH=src python3 scripts/clean_db.py
+"""
+import sys
+from pathlib import Path
+
+_backend = Path(__file__).resolve().parent.parent
+if str(_backend) not in sys.path:
+    sys.path.insert(0, str(_backend))
+
+from src.database import get_connection
+
+def main():
+    with get_connection() as conn:
+        cur = conn.cursor()
+        cur.execute("SET FOREIGN_KEY_CHECKS = 0")
+        cur.execute("TRUNCATE TABLE operation_logs")
+        cur.execute("TRUNCATE TABLE projects")
+        cur.execute("SET FOREIGN_KEY_CHECKS = 1")
+        cur.close()
+    print("已清空 operation_logs、projects 表。")
+
+if __name__ == "__main__":
+    main()