docs(deploy): add database migration step to deployment guide and create migration script

migrate.sh

@@ -0,0 +1,12 @@
+#!/bin/bash
+# 数据库迁移脚本 - 在 Docker 容器内执行 Alembic 迁移
+
+set -e
+
+CONTAINER_NAME="aether-app"
+
+echo "Running database migrations in container: $CONTAINER_NAME"
+
+docker exec $CONTAINER_NAME alembic upgrade head
+
+echo "Database migration completed successfully"