Keep guardex frontend subtree aligned with deployed compatibility metadata (#175)

The frontend compatibility fallback was already published in the standalone frontend repo, but parent guardex still had unstaged subtree drift. This commit records the same lockfile/node-version metadata in the parent tree so guardex tracks frontend state consistently.

Constraint: guardex uses tracked frontend subtree plus mirror workflow, not submodule wiring
Rejected: Convert frontend to git submodule | conflicts with documented mirror-subtree model in README
Confidence: high
Scope-risk: narrow
Reversibility: clean
Directive: For frontend runtime metadata updates, keep both standalone frontend repo and parent frontend subtree in sync
Tested: git -C frontend status --short --branch
Tested: npm run lint (frontend)
Tested: npm run build (frontend)
Not-tested: GitHub Actions mirror workflow run after this parent push

Co-authored-by: NagyVikt <nagy.viktordp@gmail.com>

Author: NagyVikt

frontend/.node-version

@@ -0,0 +1 @@
+22