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/usb.mjs

@@ -0,0 +1,22 @@
+/**
+ * @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 = [
+  ["circle", { cx: "10", cy: "7", r: "1", key: "dypaad" }],
+  ["circle", { cx: "4", cy: "20", r: "1", key: "22iqad" }],
+  ["path", { d: "M4.7 19.3 19 5", key: "1enqfc" }],
+  ["path", { d: "m21 3-3 1 2 2Z", key: "d3ov82" }],
+  ["path", { d: "M9.26 7.68 5 12l2 5", key: "1esawj" }],
+  ["path", { d: "m10 14 5 2 3.5-3.5", key: "v8oal5" }],
+  ["path", { d: "m18 12 1-1 1 1-1 1Z", key: "1bh22v" }]
+];
+const Usb = createLucideIcon("usb", __iconNode);
+
+export { __iconNode, Usb as default };
+//# sourceMappingURL=usb.mjs.map