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/bluetooth-connected.mjs

@@ -0,0 +1,18 @@
+/**
+ * @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: "m7 7 10 10-5 5V2l5 5L7 17", key: "1q5490" }],
+  ["line", { x1: "18", x2: "21", y1: "12", y2: "12", key: "1rsjjs" }],
+  ["line", { x1: "3", x2: "6", y1: "12", y2: "12", key: "11yl8c" }]
+];
+const BluetoothConnected = createLucideIcon("bluetooth-connected", __iconNode);
+
+export { __iconNode, BluetoothConnected as default };
+//# sourceMappingURL=bluetooth-connected.mjs.map