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/traverse/lib/hub.js

@@ -0,0 +1,19 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.default = void 0;
+class Hub {
+  getCode() {}
+  getScope() {}
+  addHelper() {
+    throw new Error("Helpers are not supported by the default hub.");
+  }
+  buildError(node, msg, Error = TypeError) {
+    return new Error(msg);
+  }
+}
+exports.default = Hub;
+
+//# sourceMappingURL=hub.js.map