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/arrow-up-z-a.mjs

@@ -0,0 +1,20 @@
+/**
+ * @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: "m3 8 4-4 4 4", key: "11wl7u" }],
+  ["path", { d: "M7 4v16", key: "1glfcx" }],
+  ["path", { d: "M15 4h5l-5 6h5", key: "8asdl1" }],
+  ["path", { d: "M15 20v-3.5a2.5 2.5 0 0 1 5 0V20", key: "r6l5cz" }],
+  ["path", { d: "M20 18h-5", key: "18j1r2" }]
+];
+const ArrowUpZA = createLucideIcon("arrow-up-z-a", __iconNode);
+
+export { __iconNode, ArrowUpZA as default };
+//# sourceMappingURL=arrow-up-z-a.mjs.map