fix: add provider column migration script for existing db

docs/LOCAL_DEV_RUNBOOK.md

@@ -7,6 +7,27 @@ psql "$DATABASE_URL" -f scripts/init_schema.sql
 ```
 - DB schema 檔案：[backend/scripts/init_schema.sql](../backend/scripts/init_schema.sql)
 
+如果你是 macOS 本機沒裝 `psql`，改用：
+```bash
+cd backend
+./.venv/bin/python - <<'PY'
+import psycopg
+from pathlib import Path
+sql = Path('scripts/migrate_provider_columns.sql').read_text()
+with psycopg.connect(
+    host='127.0.0.1',
+    port=54321,
+    dbname='member.ose.tw',
+    user='member_ose',
+    password='你的DB密碼'
+) as conn:
+    with conn.cursor() as cur:
+        cur.execute(sql)
+print('provider column migration done')
+PY
+```
+- 欄位改名 migration：[backend/scripts/migrate_provider_columns.sql](../backend/scripts/migrate_provider_columns.sql)
+
 ## 2) 啟動後端
 ```bash
 cd backend