build: declare @types/node only in devDependencies (#13)

* build: require Node >= 22 and build with Node 24

Add an `engines` floor of Node >= 22 to package.json and mirror it into
package-lock.json, and bump @types/node to ^24.13.3 so the typings match
the runtime the plugin is built with.

Move CI onto Node 24 (was Node 20). Raise the Debian Build-Depends floor
to nodejs (>= 22) and install Node 24 from NodeSource when building the
package.

* build: declare @types/node only in devDependencies

@types/node was listed in both dependencies and devDependencies, and the
two had drifted apart before they were aligned on ^24.13.3. It supplies
build-time typings only, so keep the devDependencies entry and drop the
duplicate.

npm already resolved it as a dev-only package, so installs are unaffected;
this just makes package.json say what npm was already doing.

Author: antobinary

package-lock.json

@@ -9,7 +9,6 @@
   "dependencies": {
     "@testing-library/react": "^13.4.0",
     "@testing-library/user-event": "^13.5.0",
-    "@types/node": "^24.13.3",
     "@types/react": "^18.2.13",
     "@types/react-dom": "^18.2.6",
     "babel-plugin-syntax-dynamic-import": "^6.18.0",