chore: allow any Node 24.x patch version in engines

[klodr]

Why

engines.node is currently pinned to the exact patch version
24.12.0. Contributors on any other 24.x patch release (24.10,
24.13, etc.) get a hard EBADENGINE error from yarn install
and have to either downgrade Node or pass --ignore-engines to
work around it.

The pin offers no real reproducibility benefit since the same
lockfile applies to every 24.x release; it just adds friction.

What

Replace the exact pin with ^24, accepting any Node 24 release.
yarn install still produces an identical dependency graph (the
lockfile is unchanged); only the engines check loosens.

   "engines": {
-    "node": "24.12.0"
+    "node": "^24"
   }

Test plan

• yarn install on Node 24.10 / 24.12 / 24.13 → succeeds
  without --ignore-engines.
• CI continues to pass (the workflow already pins Node via
  actions/setup-node, so the engines value is advisory there).
• No change for contributors already on 24.12.0.