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/clock-plus.mjs

@@ -0,0 +1,19 @@
+/**
+ * @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: "M12 6v6l3.644 1.822", key: "1jmett" }],
+  ["path", { d: "M16 19h6", key: "xwg31i" }],
+  ["path", { d: "M19 16v6", key: "tddt3s" }],
+  ["path", { d: "M21.92 13.267a10 10 0 1 0-8.653 8.653", key: "1u0osk" }]
+];
+const ClockPlus = createLucideIcon("clock-plus", __iconNode);
+
+export { __iconNode, ClockPlus as default };
+//# sourceMappingURL=clock-plus.mjs.map