fix alembic migration

api/scripts/repair_alembic_version_after_withdrawn_0020.py

@@ -0,0 +1,66 @@
+#!/usr/bin/env python3
+"""将误写入的 0020_* revision 回退到 0018，以便重新执行 0019_align_legacy_schema。
+
+用法（在 api 目录，DATABASE_URL 已配置）：
+
+    uv run python scripts/repair_alembic_version_after_withdrawn_0020.py
+    uv run python scripts/repair_alembic_version_after_withdrawn_0020.py --dry-run
+
+启动时也会自动执行同等逻辑（见 app.core.alembic_startup）。
+"""
+
+from __future__ import annotations
+
+import argparse
+import sys
+from pathlib import Path
+
+_API_DIR = Path(__file__).resolve().parents[1]
+if str(_API_DIR) not in sys.path:
+    sys.path.insert(0, str(_API_DIR))
+
+from sqlalchemy import create_engine, text
+
+from app.core.alembic_revision_repair import (
+    _WITHDRAWN_0020_REVISIONS,
+    try_repair_withdrawn_0020_revision,
+)
+from app.core.db import _database_url
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument(
+        "--dry-run",
+        action="store_true",
+        help="只检查，不写库",
+    )
+    args = parser.parse_args()
+
+    engine = create_engine(_database_url())
+    with engine.connect() as conn:
+        row = conn.execute(text("SELECT version_num FROM alembic_version")).fetchone()
+        current = row[0] if row else None
+        print(f"当前 version_num: {current!r}")
+
+        if current is None:
+            print("alembic_version 表为空，无需修复")
+            return 0
+
+        if args.dry_run:
+            if current in _WITHDRAWN_0020_REVISIONS:
+                print("[dry-run] 将回退到 0018_users_language_preference")
+            else:
+                print("无需修复")
+            return 0
+
+        if try_repair_withdrawn_0020_revision(conn):
+            conn.commit()
+            print("已回退到 0018_users_language_preference；请执行: uv run alembic upgrade head")
+        else:
+            print("无需修复")
+        return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())