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/braces.mjs

@@ -0,0 +1,26 @@
+/**
+ * @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: "M8 3H7a2 2 0 0 0-2 2v5a2 2 0 0 1-2 2 2 2 0 0 1 2 2v5c0 1.1.9 2 2 2h1", key: "ezmyqa" }
+  ],
+  [
+    "path",
+    {
+      d: "M16 21h1a2 2 0 0 0 2-2v-5c0-1.1.9-2 2-2a2 2 0 0 1-2-2V5a2 2 0 0 0-2-2h-1",
+      key: "e1hn23"
+    }
+  ]
+];
+const Braces = createLucideIcon("braces", __iconNode);
+
+export { __iconNode, Braces as default };
+//# sourceMappingURL=braces.mjs.map