Remove the #[LegacyHook] shims and procedural files for full OOP hooks in the Varbase Auth module

Problem/Motivation

The Varbase Auth hooks already live in Drupal\varbase_auth\Hook\VarbaseAuthHooks, but varbase_auth.module and includes/helpers.inc still keep #[LegacyHook] / procedural backward-compat shims that delegate to that class. For Drupal ~11.4.0 these standard hooks are invoked by core only, so the shims are redundant.

Proposed resolution

Remove the #[LegacyHook] shim in varbase_auth.module and the legacy wrapper in includes/helpers.inc, and delete both files. All logic already lives in VarbaseAuthHooks (preprocessPage() and addTemplateVariable()).

Remaining tasks

• ✅ Remove varbase_auth.module
• ✅ Remove includes/helpers.inc
• ✅ Reviewed by a human
• ✅ Release varbase-9.2.0, varbase_auth-9.2.0

API changes

The @internal legacy wrapper functions are removed; the logic remains available on the VarbaseAuthHooks service.

Release notes snippet

• task: #3608370 Remove the #[LegacyHook] shims and procedural files for full OOP hooks