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/jake/test/integration/jakelib/required_module.jake.js

@@ -0,0 +1,10 @@
+let { task, namespace } = require(`${process.env.PROJECT_DIR}/lib/jake`);
+
+namespace('usingRequire', function () {
+  task('test', () => {
+    console.log('howdy test');
+  });
+});
+
+
+