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/plug-2.mjs

@@ -0,0 +1,20 @@
+/**
+ * @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: "M9 2v6", key: "17ngun" }],
+  ["path", { d: "M15 2v6", key: "s7yy2p" }],
+  ["path", { d: "M12 17v5", key: "bb1du9" }],
+  ["path", { d: "M5 8h14", key: "pcz4l3" }],
+  ["path", { d: "M6 11V8h12v3a6 6 0 1 1-12 0Z", key: "wtfw2c" }]
+];
+const Plug2 = createLucideIcon("plug-2", __iconNode);
+
+export { __iconNode, Plug2 as default };
+//# sourceMappingURL=plug-2.mjs.map