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/layers-2.mjs

@@ -0,0 +1,29 @@
+/**
+ * @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: "M13 13.74a2 2 0 0 1-2 0L2.5 8.87a1 1 0 0 1 0-1.74L11 2.26a2 2 0 0 1 2 0l8.5 4.87a1 1 0 0 1 0 1.74z",
+      key: "15q6uc"
+    }
+  ],
+  [
+    "path",
+    {
+      d: "m20 14.285 1.5.845a1 1 0 0 1 0 1.74L13 21.74a2 2 0 0 1-2 0l-8.5-4.87a1 1 0 0 1 0-1.74l1.5-.845",
+      key: "byia6g"
+    }
+  ]
+];
+const Layers2 = createLucideIcon("layers-2", __iconNode);
+
+export { __iconNode, Layers2 as default };
+//# sourceMappingURL=layers-2.mjs.map