v2.18.19

## v2.18.19 Release Summary

This patch release includes several important security and validation fixes.

### Security fixes

* Added validation for Git repository URLs to prevent Git option injection.
* Added `--end-of-options` to Git commands to make repository URL and branch handling safer.
* Fixed branch override handling: task-level Git branch override is now applied only when the template explicitly allows it.
* Prevented custom roles from shadowing built-in role slugs such as owner or manager.
* Fixed permission resolution so built-in roles always use their built-in permissions instead of database-defined custom roles.
* Added validation to prevent access keys from being updated with a different ID or moved to another project.

### Reliability and tests

* Added tests for Git URL validation and Git command injection protection.
* Added tests for access key update validation.
* Added tests for custom role validation and reserved role slugs.
* Refactored Git branch resolution into a dedicated helper to make task behavior more consistent.