CREATE TABLE IF NOT EXISTS `conversations` (
    `id`         BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
    `user_id`    BIGINT UNSIGNED NOT NULL,
    `title`      VARCHAR(255)    NOT NULL DEFAULT 'New Chat',
    `created_at` DATETIME        NOT NULL DEFAULT CURRENT_TIMESTAMP,
    `updated_at` DATETIME        NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
    PRIMARY KEY (`id`),
    INDEX `idx_conversations_user_id` (`user_id`),
    INDEX `idx_conversations_updated_at` (`updated_at`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;