CI/CD hardening: lint, secret scan, coverage gate, auto CVE-fix PRs, GHCR + GitHub mirror publishing (#34)

- release changelog: commits rendered as description (link), divider lines dropped
- gitleaks secret scan and hadolint on every push/PR
- ruff lint/format gate (Python repos) with a pytest --cov-fail-under gate
- scheduled CRITICAL Trivy failures attempt an apk upgrade rebuild and open a follow-up PR if it clears the finding, instead of just failing red
- images also published to ghcr.io/djeex/<repo>
- a matching GitHub Release is created on the GitHub mirror, with a notice pointing back to this repo as the source of truth

tests/test_builder_utils.py

@@ -1,5 +1,3 @@
-from pathlib import Path
-
 from src.py.builder import utils
 
 
@@ -30,7 +28,7 @@ def test_load_theme_config_missing_raises(tmp_path):
     themes_dir = tmp_path / "themes"
     try:
         utils.load_theme_config("missing", themes_dir)
-        assert False, "expected FileNotFoundError"
+        raise AssertionError("expected FileNotFoundError")
     except FileNotFoundError:
         pass