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/network.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 = [
+  ["rect", { x: "16", y: "16", width: "6", height: "6", rx: "1", key: "4q2zg0" }],
+  ["rect", { x: "2", y: "16", width: "6", height: "6", rx: "1", key: "8cvhb9" }],
+  ["rect", { x: "9", y: "2", width: "6", height: "6", rx: "1", key: "1egb70" }],
+  ["path", { d: "M5 16v-3a1 1 0 0 1 1-1h12a1 1 0 0 1 1 1v3", key: "1jsf9p" }],
+  ["path", { d: "M12 12V8", key: "2874zd" }]
+];
+const Network = createLucideIcon("network", __iconNode);
+
+export { __iconNode, Network as default };
+//# sourceMappingURL=network.mjs.map