Add sync error logging, extend error flash, fix unload saves

- Log workforce sync errors to backend stdout so they appear in docker logs
- Extend error flash from 5s to 15s so errors are readable
- Replace sendBeacon (POST-only) with keepalive fetch (PUT) on unload —
  sendBeacon was hitting 404s on all three unload saves

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

frontend/node_modules/node-releases/package.json

@@ -0,0 +1,28 @@
+{
+  "name": "node-releases",
+  "version": "2.0.51",
+  "description": "Node.js releases data",
+  "type": "module",
+  "files": [
+    "data"
+  ],
+  "scripts": {
+    "build": "node scripts/build.js"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/chicoxyzzy/node-releases.git"
+  },
+  "keywords": [
+    "nodejs",
+    "releases"
+  ],
+  "author": "Sergey Rubanov <chi187@gmail.com>",
+  "license": "MIT",
+  "engines": {
+    "node": ">=18"
+  },
+  "devDependencies": {
+    "semver": "^7.3.5"
+  }
+}