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/path-parse/package.json

@@ -0,0 +1,33 @@
+{
+  "name": "path-parse",
+  "version": "1.0.7",
+  "description": "Node.js path.parse() ponyfill",
+  "main": "index.js",
+  "scripts": {
+    "test": "node test.js"
+  },
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/jbgutierrez/path-parse.git"
+  },
+  "keywords": [
+    "path",
+    "paths",
+    "file",
+    "dir",
+    "parse",
+    "built-in",
+    "util",
+    "utils",
+    "core",
+    "ponyfill",
+    "polyfill",
+    "shim"
+  ],
+  "author": "Javier Blanco <http://jbgutierrez.info>",
+  "license": "MIT",
+  "bugs": {
+    "url": "https://github.com/jbgutierrez/path-parse/issues"
+  },
+  "homepage": "https://github.com/jbgutierrez/path-parse#readme"
+}