task: #3633827 Disable telemetry in CI, DDEV and settings.php (DRUPAL_CMS_TELEMETRY=0)

Turns off Drupal CMS telemetry for this project template.

• CI: DRUPAL_CMS_TELEMETRY: "0" in the global variables, and the install job writes $settings['drupal_cms_telemetry'] = FALSE; into settings.php before site:install.
• DDEV: DRUPAL_CMS_TELEMETRY=0 in web_environment; install-varbase and init-full-automated-testing add the settings line before installing.
• README: a short Telemetry note.

The settings line is needed because a profile install does not read DRUPAL_CMS_TELEMETRY; only the Site recipe installer does.

Issue: https://www.drupal.org/i/3633827 (child of https://www.drupal.org/i/3633820)

AI-Generated: Yes

Checkpoints:

• File an issue
• Addition/Change/Update/Fix
• Testing to ensure no regression
• Automated unit testing coverage
• Automated functional testing coverage
• UX/UI designer responsibilities
• Readability
• Accessibility
• Performance
• Security
• Developer Documentation
• User Guide Documentation
• Reviewed by human
• Code review by maintainers
• Full testing and approval
• Credit contributors
• Review with the product owner
• Release notes snippet
• Release