feat(docker): 安装 tzdata 并设置 TZ=Asia/Shanghai 以让 Node.js 使用上海时区

backend/init.sql

@@ -4,7 +4,7 @@ CREATE TABLE IF NOT EXISTS emails (
     sender VARCHAR(255) NOT NULL,
     subject VARCHAR(512),
     body TEXT,
-    received_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+    received_at DATETIME,
     raw MEDIUMBLOB
 );