Release 1.1.21

fix(ci): include hidden files in templates cache artifact

The upload-artifact@v4 action excludes hidden files by default since
September 2024. This caused the templates cache shared between the
build-and-test and native-build jobs to silently strip dotfiles like
.fluxzero/, .run/, .gitignore, and .mvn/ from template directories.

As a result, native image builds produced scaffolded projects missing
all hidden directories, while the JAR and REST API (built directly
from the fresh download) worked correctly.

Added include-hidden-files: true to the templates cache upload step
and CI assertions in the native build integration test to catch this
class of regression.