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/loader-pinwheel.mjs

@@ -0,0 +1,19 @@
+/**
+ * @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: "M22 12a1 1 0 0 1-10 0 1 1 0 0 0-10 0", key: "1lzz15" }],
+  ["path", { d: "M7 20.7a1 1 0 1 1 5-8.7 1 1 0 1 0 5-8.6", key: "1gnrpi" }],
+  ["path", { d: "M7 3.3a1 1 0 1 1 5 8.6 1 1 0 1 0 5 8.6", key: "u9yy5q" }],
+  ["circle", { cx: "12", cy: "12", r: "10", key: "1mglay" }]
+];
+const LoaderPinwheel = createLucideIcon("loader-pinwheel", __iconNode);
+
+export { __iconNode, LoaderPinwheel as default };
+//# sourceMappingURL=loader-pinwheel.mjs.map