chore: tighten engines.node floor to >=20.19.0

ESLint 10 and chokidar 5 both require Node >=20.19.0.
CI already tests Node 20 (latest) and 22, both satisfy this.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: sjsyrek

package.json

@@ -57,7 +57,7 @@
   "author": "DeepL SE",
   "license": "MIT",
   "engines": {
-    "node": ">=20.0.0",
+    "node": ">=20.19.0",
     "npm": ">=9.0.0"
   },
   "dependencies": {