How do you implement a page template automatically being applied to a page?

The easiest way to achieve your desired result is to create a template file in your child theme and name it page.php.
WordPress has a template hierarchy for template selection based on the queried object. See documentation.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)