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/tablet-smartphone.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 = [
+  ["rect", { width: "10", height: "14", x: "3", y: "8", rx: "2", key: "1vrsiq" }],
+  ["path", { d: "M5 4a2 2 0 0 1 2-2h12a2 2 0 0 1 2 2v16a2 2 0 0 1-2 2h-2.4", key: "1j4zmg" }],
+  ["path", { d: "M8 18h.01", key: "lrp35t" }]
+];
+const TabletSmartphone = createLucideIcon("tablet-smartphone", __iconNode);
+
+export { __iconNode, TabletSmartphone as default };
+//# sourceMappingURL=tablet-smartphone.mjs.map