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/spell-check-2.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: "m6 16 6-12 6 12", key: "1b4byz" }],
+  ["path", { d: "M8 12h8", key: "1wcyev" }],
+  [
+    "path",
+    {
+      d: "M4 21c1.1 0 1.1-1 2.3-1s1.1 1 2.3 1c1.1 0 1.1-1 2.3-1 1.1 0 1.1 1 2.3 1 1.1 0 1.1-1 2.3-1 1.1 0 1.1 1 2.3 1 1.1 0 1.1-1 2.3-1",
+      key: "8mdmtu"
+    }
+  ]
+];
+const SpellCheck2 = createLucideIcon("spell-check-2", __iconNode);
+
+export { __iconNode, SpellCheck2 as default };
+//# sourceMappingURL=spell-check-2.mjs.map