CREATE TABLE system_settings (
    id            BIGINT NOT NULL,
    setting_key   VARCHAR(128) NOT NULL,
    setting_value TEXT,
    updated_at    DATETIME(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) ON UPDATE CURRENT_TIMESTAMP(3),
    updated_by    BIGINT DEFAULT NULL,
    PRIMARY KEY (id),
    UNIQUE KEY uk_system_setting_key (setting_key)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci COMMENT='Platform-level key-value settings';
