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/key.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: "m15.5 7.5 2.3 2.3a1 1 0 0 0 1.4 0l2.1-2.1a1 1 0 0 0 0-1.4L19 4", key: "g0fldk" }],
+  ["path", { d: "m21 2-9.6 9.6", key: "1j0ho8" }],
+  ["circle", { cx: "7.5", cy: "15.5", r: "5.5", key: "yqb3hr" }]
+];
+const Key = createLucideIcon("key", __iconNode);
+
+export { __iconNode, Key as default };
+//# sourceMappingURL=key.mjs.map