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/runtime/helpers/tsRewriteRelativeImportExtensions.js

@@ -0,0 +1,6 @@
+function tsRewriteRelativeImportExtensions(t, e) {
+  return "string" == typeof t && /^\.\.?\//.test(t) ? t.replace(/\.(tsx)$|((?:\.d)?)((?:\.[^./]+)?)\.([cm]?)ts$/i, function (t, s, r, n, o) {
+    return s ? e ? ".jsx" : ".js" : !r || n && o ? r + n + "." + o.toLowerCase() + "js" : t;
+  }) : t;
+}
+module.exports = tsRewriteRelativeImportExtensions, module.exports.__esModule = true, module.exports["default"] = module.exports;