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/regenerate/package.json

@@ -0,0 +1,38 @@
+{
+  "name": "regenerate",
+  "version": "1.4.2",
+  "description": "Generate JavaScript-compatible regular expressions based on a given set of Unicode symbols or code points.",
+  "homepage": "https://mths.be/regenerate",
+  "main": "regenerate.js",
+  "keywords": [
+    "regex",
+    "regexp",
+    "javascript",
+    "unicode",
+    "generator",
+    "tool"
+  ],
+  "license": "MIT",
+  "author": {
+    "name": "Mathias Bynens",
+    "url": "https://mathiasbynens.be/"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/mathiasbynens/regenerate.git"
+  },
+  "bugs": "https://github.com/mathiasbynens/regenerate/issues",
+  "scripts": {
+    "cover": "istanbul cover --report html --verbose --dir coverage tests/tests.js",
+    "test": "node tests/tests.js"
+  },
+  "devDependencies": {
+    "codecov": "^1.0.1",
+    "grunt": "^0.4.5",
+    "grunt-shell": "^1.1.1",
+    "istanbul": "^0.4.3",
+    "qunit-extras": "^1.1.0",
+    "qunitjs": "~1.11.0",
+    "requirejs": "^2.1.15"
+  }
+}