feat: init_db自动执行SQL迁移脚本

数据库初始化时自动执行sql目录下的迁移脚本，支持幂等执行：
- 遍历sql/*.sql文件按顺序执行
- 忽略重复字段/索引错误（MySQL 1060/1061）
- 输出执行的迁移文件列表

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

backend/init_db.py

@@ -2,6 +2,7 @@
 from pathlib import Path
 
 import pymysql
+from pymysql import MySQLError
 
 from app import create_app
 from app.extensions import db
@@ -12,6 +13,7 @@ from app.models import DetectionConfig, SpamTrainingSample, User
 BASE_DIR = Path(__file__).resolve().parent
 MYSQL_CONFIG_PATH = BASE_DIR / "mysqlconfig.json"
 SPAM_SEED_PATH = BASE_DIR / "seed" / "spam_samples_seed.json"
+SQL_MIGRATIONS_DIR = BASE_DIR / "sql"
 
 
 def load_mysql_cfg() -> dict:
@@ -39,6 +41,46 @@ def create_database(mysql_cfg: dict) -> None:
         conn.close()
 
 
+def run_sql_migrations(mysql_cfg: dict) -> list[str]:
+    """执行 sql 目录下的迁移脚本"""
+    if not SQL_MIGRATIONS_DIR.exists():
+        return []
+
+    conn = pymysql.connect(
+        host=mysql_cfg.get("host", "127.0.0.1"),
+        port=int(mysql_cfg.get("port", 3306)),
+        user=mysql_cfg["user"],
+        password=mysql_cfg["password"],
+        database=mysql_cfg["database"],
+        charset=mysql_cfg.get("charset", "utf8mb4"),
+        autocommit=True,
+    )
+
+    executed = []
+    try:
+        with conn.cursor() as cursor:
+            sql_files = sorted(SQL_MIGRATIONS_DIR.glob("*.sql"))
+            for sql_file in sql_files:
+                sql_content = sql_file.read_text(encoding="utf-8")
+                statements = [s.strip() for s in sql_content.split(";") if s.strip() and not s.strip().startswith("--")]
+                for stmt in statements:
+                    if stmt:
+                        try:
+                            cursor.execute(stmt)
+                        except MySQLError as e:
+                            if "1060" in str(e):
+                                pass
+                            elif "1061" in str(e):
+                                pass
+                            else:
+                                print(f"SQL 警告 ({sql_file.name}): {e}")
+                executed.append(sql_file.name)
+    finally:
+        conn.close()
+
+    return executed
+
+
 def ensure_seed_file() -> None:
     if SPAM_SEED_PATH.exists():
         return
@@ -135,6 +177,7 @@ def main():
     app = create_app()
     with app.app_context():
         db.create_all()
+        migrations = run_sql_migrations(mysql_cfg)
         created, updated = seed_samples()
         threshold = ensure_detection_config(mysql_cfg)
         admin_msg = init_admin(mysql_cfg)
@@ -146,6 +189,8 @@ def main():
     print(f"- 初始阈值: {threshold}")
     print(f"- {admin_msg}")
     print(f"- 模型版本: {model_meta.get('version')}")
+    if migrations:
+        print(f"- SQL迁移: {', '.join(migrations)}")
 
 
 if __name__ == "__main__":