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/navigation-2-off.mjs

@@ -0,0 +1,18 @@
+/**
+ * @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: "M9.31 9.31 5 21l7-4 7 4-1.17-3.17", key: "qoq2o2" }],
+  ["path", { d: "M14.53 8.88 12 2l-1.17 3.17", key: "k3sjzy" }],
+  ["line", { x1: "2", x2: "22", y1: "2", y2: "22", key: "a6p6uj" }]
+];
+const Navigation2Off = createLucideIcon("navigation-2-off", __iconNode);
+
+export { __iconNode, Navigation2Off as default };
+//# sourceMappingURL=navigation-2-off.mjs.map