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/lucide-react/dist/esm/icons/traffic-cone.mjs

@@ -0,0 +1,25 @@
+/**
+ * @license lucide-react v1.24.0 - ISC
+ *
+ * This source code is licensed under the ISC license.
+ * See the LICENSE file in the root directory of this source tree.
+ */
+
+import createLucideIcon from '../createLucideIcon.mjs';
+
+const __iconNode = [
+  ["path", { d: "M16.05 10.966a5 2.5 0 0 1-8.1 0", key: "m5jpwb" }],
+  [
+    "path",
+    {
+      d: "m16.923 14.049 4.48 2.04a1 1 0 0 1 .001 1.831l-8.574 3.9a2 2 0 0 1-1.66 0l-8.574-3.91a1 1 0 0 1 0-1.83l4.484-2.04",
+      key: "rbg3g8"
+    }
+  ],
+  ["path", { d: "M16.949 14.14a5 2.5 0 1 1-9.9 0L10.063 3.5a2 2 0 0 1 3.874 0z", key: "vap8c8" }],
+  ["path", { d: "M9.194 6.57a5 2.5 0 0 0 5.61 0", key: "15hn5c" }]
+];
+const TrafficCone = createLucideIcon("traffic-cone", __iconNode);
+
+export { __iconNode, TrafficCone as default };
+//# sourceMappingURL=traffic-cone.mjs.map