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/stamp.mjs

@@ -0,0 +1,24 @@
+/**
+ * @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: "M14 13V8.5C14 7 15 7 15 5a3 3 0 0 0-6 0c0 2 1 2 1 3.5V13", key: "i9gjdv" }],
+  [
+    "path",
+    {
+      d: "M20 15.5a2.5 2.5 0 0 0-2.5-2.5h-11A2.5 2.5 0 0 0 4 15.5V17a1 1 0 0 0 1 1h14a1 1 0 0 0 1-1z",
+      key: "1vzg3v"
+    }
+  ],
+  ["path", { d: "M5 22h14", key: "ehvnwv" }]
+];
+const Stamp = createLucideIcon("stamp", __iconNode);
+
+export { __iconNode, Stamp as default };
+//# sourceMappingURL=stamp.mjs.map