Replace eZ Systems / eZ Publish references with Exponential / 7x:
- page_copyright.tpl: 'eZ Publish' → 'Exponential', ez.no → exponential.earth / se7enx.com,
  copyright year 1999-2014 → 1998-2026
- page_login_copyright.tpl: same rebrand, updated i18n hash parameters and URLs

Applies to 2.x (Ibexa 4.x / eZ Platform 3.x compatible branch).