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/@babel/template/README.md

@@ -0,0 +1,19 @@
+# @babel/template
+
+> Generate an AST from a string template.
+
+See our website [@babel/template](https://babeljs.io/docs/babel-template) for more information or the [issues](https://github.com/babel/babel/issues?utf8=%E2%9C%93&q=is%3Aissue+label%3A%22pkg%3A%20template%22+is%3Aopen) associated with this package.
+
+## Install
+
+Using npm:
+
+```sh
+npm install --save-dev @babel/template
+```
+
+or using yarn:
+
+```sh
+yarn add @babel/template --dev
+```