feat(audit): 新增 L2 审计脚本与作者补丁脚本

+#!/usr/bin/env python3
+"""补处理 merge+skipped 中 merge_authors=1 的 60 条记录。
+
+暂存表 matched_song_id 存的是 source_song_id，通过 source_song_id 找到
+目标库实际记录，再做作者字段增量合并。
+"""
+
+from __future__ import annotations
+
+import os
+import sys
+from pathlib import Path
+
+import pymysql
+from dotenv import load_dotenv
+
+sys.path.insert(0, str(Path(__file__).resolve().parent))
+from import_hk_songs import _merge_author_field
+
+load_dotenv()
+
+TARGET_DB_CONFIG = {
+    "host": os.getenv("TARGET_DB_HOST"),
+    "port": int(os.getenv("TARGET_DB_PORT", 3306)),
+    "user": os.getenv("TARGET_DB_USER"),
+    "password": os.getenv("TARGET_DB_PASSWORD"),
+    "database": os.getenv("TARGET_DB_NAME"),
+    "charset": "utf8mb4",
+    "cursorclass": pymysql.cursors.DictCursor,
+}
+TABLE = os.getenv("TARGET_TABLE_NAME", "hk_songs")
+STAGING = "hk_songs_import_staging"
+
+
+def main(dry_run: bool = False) -> None:
+    conn = pymysql.connect(**TARGET_DB_CONFIG)
+    try:
+        # 1. 拉取所有需要补作者合并的暂存记录
+        with conn.cursor() as cur:
+            cur.execute(f"""
+                SELECT staging_id, matched_song_id, lyricist, composer
+                FROM `{STAGING}`
+                WHERE dedup_action = 'merge'
+                  AND staging_status = 'skipped'
+                  AND merge_authors = 1
+                ORDER BY staging_id
+            """)
+            staging_rows = cur.fetchall()
+
+        print(f"待处理记录数: {len(staging_rows)}")
+
+        # 2. 批量查目标库（按 source_song_id）
+        source_ids = [r["matched_song_id"] for r in staging_rows if r["matched_song_id"]]
+        ph = ",".join(["%s"] * len(source_ids))
+        with conn.cursor() as cur:
+            cur.execute(
+                f"SELECT id, name, lyricist, composer, source_song_id FROM `{TABLE}` WHERE source_song_id IN ({ph})",
+                source_ids,
+            )
+            target_rows = {str(r["source_song_id"]): r for r in cur.fetchall()}
+
+        print(f"目标库命中: {len(target_rows)} / {len(source_ids)}")
+
+        # 3. 计算合并结果
+        updates: list[dict] = []
+        skipped: list[dict] = []
+
+        for s in staging_rows:
+            sid = s["matched_song_id"]
+            target = target_rows.get(str(sid))
+            if not target:
+                skipped.append({"staging_id": s["staging_id"], "source_song_id": sid, "reason": "目标库未找到"})
+                continue
+
+            merged_lyricist = _merge_author_field(target["lyricist"], s["lyricist"])
+            merged_composer = _merge_author_field(target["composer"], s["composer"])
+
+            lyricist_changed = bool(merged_lyricist) and merged_lyricist != (target["lyricist"] or "")
+            composer_changed = bool(merged_composer) and merged_composer != (target["composer"] or "")
+
+            if not lyricist_changed and not composer_changed:
+                skipped.append({"staging_id": s["staging_id"], "source_song_id": sid, "reason": "合并后无变化"})
+                continue
+
+            updates.append({
+                "target_id": target["id"],
+                "name": target["name"],
+                "source_song_id": sid,
+                "staging_id": s["staging_id"],
+                "orig_lyricist": target["lyricist"],
+                "orig_composer": target["composer"],
+                "new_lyricist": merged_lyricist if lyricist_changed else None,
+                "new_composer": merged_composer if composer_changed else None,
+                "staging_lyricist": s["lyricist"],
+                "staging_composer": s["composer"],
+            })
+
+        print(f"\n需要 UPDATE: {len(updates)} 条")
+        print(f"无需操作:    {len(skipped)} 条")
+
+        if dry_run:
+            print("\n[dry-run] 预览变更（前 20 条）:")
+            for u in updates[:20]:
+                print(f"  id={u['target_id']} name={u['name']}")
+                if u["new_lyricist"] is not None:
+                    print(f"    lyricist: {u['orig_lyricist']!r} -> {u['new_lyricist']!r}")
+                if u["new_composer"] is not None:
+                    print(f"    composer: {u['orig_composer']!r} -> {u['new_composer']!r}")
+            return
+
+        # 4. 执行 UPDATE
+        updated = 0
+        errors = 0
+        with conn.cursor() as cur:
+            for u in updates:
+                try:
+                    if u["new_lyricist"] is not None:
+                        cur.execute(
+                            f"UPDATE `{TABLE}` SET lyricist = %s WHERE id = %s",
+                            (u["new_lyricist"], u["target_id"]),
+                        )
+                    if u["new_composer"] is not None:
+                        cur.execute(
+                            f"UPDATE `{TABLE}` SET composer = %s WHERE id = %s",
+                            (u["new_composer"], u["target_id"]),
+                        )
+                    updated += 1
+                except Exception as e:
+                    errors += 1
+                    print(f"  [错误] target_id={u['target_id']}: {e}")
+
+        conn.commit()
+        print(f"\n完成: 已更新 {updated} 条，错误 {errors} 条")
+
+        if skipped:
+            print(f"\n无需操作的 {len(skipped)} 条:")
+            for s in skipped:
+                print(f"  staging_id={s['staging_id']} source_song_id={s['source_song_id']} 原因={s['reason']}")
+
+    finally:
+        conn.close()
+
+
+if __name__ == "__main__":
+    import argparse
+    parser = argparse.ArgumentParser(description="补处理 merge+skipped 作者合并")
+    parser.add_argument("--dry-run", action="store_true", help="只预览，不写库")
+    args = parser.parse_args()
+    main(dry_run=args.dry_run)